Review and a New Design of the Chart of Nuclides
Yinfang LUO, Xinliang YAN, Meng WANG, Qian WANG, Xiaohong ZHOU
The chart of the nuclides is one of the fundamental tools in nuclear science and technology. In this paper, we present a new two-dimensional chart of the nuclides, which displays up-to-date ground state nuclear properties such as isotopic abundances of stable nuclei, decay modes, half-life of radioactive nuclei, atomic mass error, and other experimental information extracted from the latest atomic mass evaluation AME2020 and NUBASE2020 evaluation of nuclear physics properties. We review the current status and trends in the visualization of nuclear charts, taking the Karlsruher Nuklidkarte as an example. We discuss the brief history and future perspectives of isotope discovery and nuclear chart publication, followed by the design details of our new chart of the nuclides. Additionally, we recommend free and open-source nuclear chart plotting software/websites. Our newly designed chart of the nuclides will be available in printed versions, including a wall chart and an A4-size folded chart for desktop usage. We plan to update the printed charts synchronously with the AME and NUBASE publications. This will ensure that the charts serve as a regular medium for the concise presentation of the NUBASE database.
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Correlation Between Neutron Star Observation and Equation of State of Nuclear Matter at Different Densities
Jing ZHANG, Dehua WEN
Neutron star matter is mainly composed of asymmetric dense nuclear matter. At present, there is still great uncertainty in the understanding of the high-density asymmetric nuclear matter through the terrestrial experiments, such as the heavy ion collisions. With the improvement of astronomical observation accuracy and the increase of observable measurements of neutron stars, it is possible to reverse constraint the state of high-density nuclear matter based on astronomical observation of neutron stars. Theoretically investigating the correlation between the observable measurements of neutron stars and the equation of states (EOSs) at different density sections will be helpful to the research of the reverse constraints. In this work, by employing the piecewise polytrope EOSs, the observable measurements of the radius(R), tidal deformability($\varLambda$ ), moment of inertia(I) of the neutron star $etc$ . are calculated and analyzed, and the correlations between these observations and each density segment of the EOSs are given. The results show that tidal deformability ($\varLambda$ ) and f-mode frequency ($\nu$ ) of a canonical neutron star ($M \!=\! 1.4\, M_{\odot}$ ) are mainly correlated with $0.5\rho_{\rm{sat}} \!\sim\! 1.5\rho_{ sat}$ , $2.5\rho_{\rm{sat}} \!\sim\! 3.5\rho_{\rm{sat}}$ and $3.5\rho_{\rm{sat}} \!\sim\! 4.5\rho_{\rm{sat}}$ segments of EOSs; the neutron star radius (R) are mainly correlated with $1.5\rho_{\rm{sat}} \!\sim\! 3.5\rho_{\rm{sat}}$ and the crust segments of EOSs; the moment of inertia (I) are mainly correlated with the density below $ 4.5\rho_{\rm{sat}}$ segments of EOSs.
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Probing Clustering Configurations of 16O by the Yield Distribution in Heavy Ion Collisions at Fermi Energy
Chenchen GUO, Wanbing HE, Zhendong AN, Jun SU, Long ZHU, Lijuan WU
In recent years, the cluster structure in nuclei has attracted a lot of attention. The goal of this work is to investigate the yield distribution of heavy ion collisions at Fermi energy and evaluate the $\alpha$ cluster configurations in light nuclei. The 16O+16O reactions with four different initialization $\alpha$ configurations (long chain, kite, square, tetrahedron)are simulated based on the Extended Quantum Molecular Dynamics (EQMD) transport model. The nuclei with different structures are investigated by observation of the multiplicity distribution of yields in nuclear reactions. It is found that the yields of free protons and 4He were affected by different cluster configurations, which indicates that 4He/proton can be used as a characterization of cluster structure. In addition, the $\alpha$ cluster configuration information of 16O can be extracted from the outgoing $\theta$ and $\phi$ and the kinetic energy spectrum of of free protons and 4He.
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An Overview and Prospect of Nuclear Battery
Xiaoyi LI, Jingbin LU, Renzhou ZHENG, Xu XU, Yu WANG, Yumin LIU, Rui HE, Lei LIANG
The nuclear battery has many advantages, including high energy density, stable performance, no manual intervention etc., which can be widely utilized in cases requiring long-term reliable power supply. Among them, the Radioisotope Thermoelectric Generators (RTG) is the earliest used and the most technically matured one, while betavoltaic battery is now commercialized. However, there are still some problems including self-absorption effect, low energy conversion efficiency and severe radiation damage which restrict the application of betavoltaic batteries. Additionally, for an actual nuclear battery, it should be noticed that the component and density of the source will be changed because the radiation source decays continually, which leads to the electrical performance decline. In this review, the major events in nuclear battery development are listed on a timeline, and the principles and applications of different types of nuclear batteries are also introduced. For betavoltaic battery, the existence of self-absorption effect is pointed out as an important scientific problem, and for batteries with 63Ni and TiT2 source, the time-related electrical properties are also obtained. This paper also pointed out that, fine and precise calculations are very crucial in the optimized designing processes for a particular structure of the practical nuclear battery. Finally, researching assumptions including combining the source and the energy converting material and the use of energy converting structures with heavier isotopes are presented, which are benefit to solve the self-absorption problem, rise the output power of the nuclear battery and reduce the influence of radiation damage.
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Transport of Isospin Degree of Freedom in Heavy Ion Reactions and the Constraint of Symmetry Energy
Zhigang XIAO
Heavy ion reactions provide an effective tool to study the nuclear equation of state (EOS) in terristial laborartory. When the number of neutrons differs largely with the number of protons in a nuclear system or nuclei, the main contribution to the nuclear EOS comes from the symmetry energy term. The nuclear symmetry energy, reflecting the isovector sector of the nucleon-nucleon potential, is closely relevant to the structural properties of dense object and the merging process in stellar environments, as well as to the exotic properties of nuclei and the location of the board of nuclear chart. However, the density dependence of the nuclear symmetry energy is the most unknown ingredient in the properties of nuclear matter so far. Thus the investigation of nuclear symmetry energy in wide density range becomes the main frontiers in many world-level nuclear laboratories and astrophyics observatories. In this article, we review briefly the experimental progress in this field. Particularly the experimental studies on the transport of the isospin degree of freedom in heavy ion reactions and the constraint of nuclear symmetry energy based on the Heavy Ion Research Facity at Lanzhou (HIRFL) are introduced. It has been shown that the isospin drift process persists to the late stage of the reaction, indicating that the isospin transport time scale may depend on the physics process under investigation. Due to the long-time accumulation of isospin effects, the angular distribution of the isospin concentration of the light particles in a wide range of angle is a sensitive probe of nuclear symmetry energy. With ${S}\!=\!28.3\,\mathrm{M}\mathrm{e}\mathrm{V}$ fixed at saturation point, the slope of the symmetry energy depending on density is contrained in the range of $L\!=\!33\!\sim\!61\,\mathrm{M}\mathrm{e}\mathrm{V}$ at $ \mathrm{C}\mathrm{L}\!=\!95$ %. Using a Compact Spectrometer for Havy Ion Experiment (CSHINE) with ability to achieve isotopic particle identification and fission event reconstruction, the small angle correlation function of the isotope-resolved light charged particles can be measured to derive the time scale of isospin relaxation in heavy ion reactions at Fermi energies. In the last section of the article, the isovector orientation effect of the polarized deuteron beam scattering off heavy target is introduced, which offers a novel means to constrain the nuclear symmetry energy below saturation density.
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MAGIC: Matter in Astrophysics, Gravitational Waves, and Ion Collisions
Motornenko Anton, Hanauske Matthias, Weih Lukas, Steinheimer Jan, Stöcker Horst
The gravitational waves emitted from a binary neutron star merger, as predicted from general relativistic magneto-hydrodynamics calculations, are sensitive to the appearance of quark matter and the stiffness of the equation of state of QCD matter present in the inner cores of the stars. These astrophysically created extremes of thermodynamics do match, to within 20%, the values of densities and temperatures which are found in relativistic heavy ion collisions, if though at quite different rapidity windows, impact parameters and bombarding energies of the heavy nuclear systems. In this article we combine the results obtained in general relativistic simulations of binary neutron star systems with ones from heavy ion collisions in the lab to pin down the EOS and the phase structure of dense matter. We discuss that the postmerger gravitational wave emission of the neutron star merger remnant might give, in the near future, insides about the properties of the hadron quark transition.
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Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
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doi: 10.11804/NuclPhysRev.41.2023065
Abstract:
In this work, we presented the test results for a prototype of plastic scintillation detectors for time-of-flight measurement, aiming to provide preliminary research for the future development of time-of-flight detectors for HIAFHFRS facility. Each timing detectors was composed of a fast scintillating plastic and four fast photomultiplier tubes coupled to its four sides. The time performance of the detectors was tested using pico-second pulsed laser, For two plastic scintillation detectors with different sizes, a pico-second pulsed laser was used to simulating the actual ionbeam situation by changing laser’s parameters including spot size, repetition rate, light intensity and hitting position. The data was processed utilizing CAEN-DT5742 digitizer and Mesytec-MCFD16+MTDC32 electronics. When the focused laser hit at the center of the plastic scintillators, the time-of-flight (ToF) resolution of two small-sized (7 cm×7cm)plastic scintillation detectors could reach 8 ps, whereas the ToF resolution of the small and large (26 cm×10 cm) detectors could achieve 12 ps. After varying the parameters of the laser, the corresponding ToF resolutions were found to be in the range of 10–16 ps and 19–46 ps, respectively. The ToF resolutions from the test meets the timing-resolution requirement of the HFRS beamline, thereby establishing a solid foundation for further optimizing the time-of-flight detectors.
Column
- Contents
- Insert page
- Invited Plenary Presentations
- Reports from the Winners of the “Hu Jimin Award of Education and Science”
- Parallel Session Presentations-Nuclear structure
- Parallel Session Presentations-Nuclear astrophysics
- Parallel Session Presentations-Low energy nuclear reaction
- Parallel Session Presentations-Machine learning in nuclear physics
- Parallel Session Presentations-Accelerator and nuclear technology
- Parallel Session Presentations-Accelerator and nuclear technology
- Parallel Session Presentations-Intermediate and high energy nuclear physics
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2024, 41(1): 1-10.
doi: 10.11804/NuclPhysRev.41.2023CNPC55
Abstract:
The chiral magnetic effect (CME) refers to a charge separation along a strong magnetic field due to an imbalanced chirality of quarks from interactions with the vacuum topological gluon field. This chiral anomaly is a fundamental property of quantum chromodynamics (QCD) and, therefore, an observation of the CME would have far-reaching impact on our understanding of QCD and Nature. The measurements of the CME-sensitive azimuthal correlator Δγ observable in heavy-ion collisions are contaminated by a major background induced by elliptic flow anisotropy. Several novel approaches have been carried out, including a dedicated isobar collision program, to address this flow-induced background. Further background effects, arising from nonflow correlations, have been studied. While the isobar data are consistent with zero CME signal with an upper limit of 10% of the measured Δγ, the Au+Au midcentral data suggest a positive CME signal on the order of 10% of the measured Δγ with a significance of ~2 standard deviations. Future increased statistics and improved detector capability should yield a firm conclusion on the existence (or the lack) of the CME in relativistic heavy-ion collisions.
The chiral magnetic effect (CME) refers to a charge separation along a strong magnetic field due to an imbalanced chirality of quarks from interactions with the vacuum topological gluon field. This chiral anomaly is a fundamental property of quantum chromodynamics (QCD) and, therefore, an observation of the CME would have far-reaching impact on our understanding of QCD and Nature. The measurements of the CME-sensitive azimuthal correlator Δγ observable in heavy-ion collisions are contaminated by a major background induced by elliptic flow anisotropy. Several novel approaches have been carried out, including a dedicated isobar collision program, to address this flow-induced background. Further background effects, arising from nonflow correlations, have been studied. While the isobar data are consistent with zero CME signal with an upper limit of 10% of the measured Δγ, the Au+Au midcentral data suggest a positive CME signal on the order of 10% of the measured Δγ with a significance of ~2 standard deviations. Future increased statistics and improved detector capability should yield a firm conclusion on the existence (or the lack) of the CME in relativistic heavy-ion collisions.
2024, 41(1): 11-19.
doi: 10.11804/NuclPhysRev.41.2023CNPC59
Abstract:
The 12C(α, γ)16O reaction is one of the most important reactions in nuclear astrophysics. It greatly influences the ratio of the abundances for the carbon and oxygen created at the end of the helium burning by competing with the triple-α process. It is of great significance for understanding both stellar and biological evolution, as well as for studying black hole gaps. It is called the Holy Grail reaction in nuclear astrophysics. In this article, the current research status of this reaction and future plans were introduced. There are several indirect methods to measure this reaction, such as elastic scattering, β-delayed α decay of 16N, inverse reactions and α transfer reactions. In recent years, there were also some direct measurement experiments. However, these studies couldn’t make the measurement entering inside the Gamow Window. There are also differences between different indirect measurement results. The uncertainty of this reaction is still much larger than the critical value of 10%, which is required by the nuclear astrophysics calculation. Therefore, the measurement of this reaction remains a focus of attention in nuclear astrophysics. The RNB group in China Institute of Atomic Energy used the (11B, 7Li) transfer reaction to study the 12C(α, γ)16O reaction and are working on the direct experiment in Jinping underground nuclear astrophysics laboratory. The lowest energy experiment has been finished and the measurement for lower energy will be performed in the future.
The 12C(α, γ)16O reaction is one of the most important reactions in nuclear astrophysics. It greatly influences the ratio of the abundances for the carbon and oxygen created at the end of the helium burning by competing with the triple-α process. It is of great significance for understanding both stellar and biological evolution, as well as for studying black hole gaps. It is called the Holy Grail reaction in nuclear astrophysics. In this article, the current research status of this reaction and future plans were introduced. There are several indirect methods to measure this reaction, such as elastic scattering, β-delayed α decay of 16N, inverse reactions and α transfer reactions. In recent years, there were also some direct measurement experiments. However, these studies couldn’t make the measurement entering inside the Gamow Window. There are also differences between different indirect measurement results. The uncertainty of this reaction is still much larger than the critical value of 10%, which is required by the nuclear astrophysics calculation. Therefore, the measurement of this reaction remains a focus of attention in nuclear astrophysics. The RNB group in China Institute of Atomic Energy used the (11B, 7Li) transfer reaction to study the 12C(α, γ)16O reaction and are working on the direct experiment in Jinping underground nuclear astrophysics laboratory. The lowest energy experiment has been finished and the measurement for lower energy will be performed in the future.
2024, 41(1): 20-25.
doi: 10.11804/NuclPhysRev.41.2023CNPC41
Abstract:
The huge orbital angular momentum generated by non-central relativistic heavy-ion collisions in the reaction zone can be transferred to the quark-gluon plasma (QGP) in the form of fluid vortices. Partons in the QGP will be polarized along the angular momentum through the spin-orbit interaction, the so-called “Globla Polarization”. After nearly two decades of exploration, experimental data on the global polarization of Λ hyperons and ϕ, K*0 vector mesons in heavy-ion collisions have confirmed a new phenomenon of QGP global polarization, which has attracted widespread attention from researchers and become a new hot direction in the forefront of high-energy nuclear physics. This paper briefly describe the experimental measurements of global polarization in heavy-ion collisions, focusing on the global polarization of Λ hyperons and the spin alignment of ϕ, K*0 mesons, followed by a brief discussion of the physics information provided by the experimental data.
The huge orbital angular momentum generated by non-central relativistic heavy-ion collisions in the reaction zone can be transferred to the quark-gluon plasma (QGP) in the form of fluid vortices. Partons in the QGP will be polarized along the angular momentum through the spin-orbit interaction, the so-called “Globla Polarization”. After nearly two decades of exploration, experimental data on the global polarization of Λ hyperons and ϕ, K*0 vector mesons in heavy-ion collisions have confirmed a new phenomenon of QGP global polarization, which has attracted widespread attention from researchers and become a new hot direction in the forefront of high-energy nuclear physics. This paper briefly describe the experimental measurements of global polarization in heavy-ion collisions, focusing on the global polarization of Λ hyperons and the spin alignment of ϕ, K*0 mesons, followed by a brief discussion of the physics information provided by the experimental data.
2024, 41(1): 26-34.
doi: 10.11804/NuclPhysRev.41.2023CNPC39
Abstract:
The basic properties of atomic nuclei including spins, magnetic moments, electric quadrupole moments and charge radii, are sensitive probes to different aspects of exotic nuclear structure, and are also important to investigate the unrevealed nature of interaction between nucleons. Based on multidiscipline, laser spectroscopy is a unique tool to precisely measure the basic nuclear properties mentioned above in a nuclear-model independent way by measuring the hyperfine structure of atoms, ions, or molecules, which has played an important role in the study of exotic nuclear structures across the different regions of the nuclear chart. Basic principles of laser spectroscopy and various types of experimental devices are expounded after the brief history of the hyperfine structure. Furthermore, advantages of utilizing laser spectroscopy in the study of nuclear structure are briefly introduced by taking the radioactive neutron-deficient Pb region as an illustration. In addition, current condition of collinear laser spectroscopy setup has been systematically reviewed, together with the latest progress on collinear resonance ionization spectroscopy offline devices at Peking University. Finally, the developing status and ongoing plan of laser spectroscopy devices for current and future radioactive ion beam facilities in China have been put forward, and the broad prospects of laser spectroscopy in unstable nuclear properties and the fundamental symmetries based on molecular spectroscopy are interpreted.
The basic properties of atomic nuclei including spins, magnetic moments, electric quadrupole moments and charge radii, are sensitive probes to different aspects of exotic nuclear structure, and are also important to investigate the unrevealed nature of interaction between nucleons. Based on multidiscipline, laser spectroscopy is a unique tool to precisely measure the basic nuclear properties mentioned above in a nuclear-model independent way by measuring the hyperfine structure of atoms, ions, or molecules, which has played an important role in the study of exotic nuclear structures across the different regions of the nuclear chart. Basic principles of laser spectroscopy and various types of experimental devices are expounded after the brief history of the hyperfine structure. Furthermore, advantages of utilizing laser spectroscopy in the study of nuclear structure are briefly introduced by taking the radioactive neutron-deficient Pb region as an illustration. In addition, current condition of collinear laser spectroscopy setup has been systematically reviewed, together with the latest progress on collinear resonance ionization spectroscopy offline devices at Peking University. Finally, the developing status and ongoing plan of laser spectroscopy devices for current and future radioactive ion beam facilities in China have been put forward, and the broad prospects of laser spectroscopy in unstable nuclear properties and the fundamental symmetries based on molecular spectroscopy are interpreted.
2024, 41(1): 35-50.
doi: 10.11804/NuclPhysRev.41.2023CNPC71
Abstract:
Understanding the nucleon-nucleon interaction in free space and in medium has always been one of the most important topics in nuclear physics. It is also one of the most important objectives of large scientific facilities such as HIAF and FRIB. Understanding nuclear structure, reactions, and the properties of dense stars from ab initio calculations based on nucleon degrees of freedom and microscopic nuclear forces has always been a primary goal pursued by nuclear physicists. First proposed by Nobel laureate Weinberg in 1990s and developed by joint efforts of scientists around the world, the Weinberg chiral nuclear force has now been the de facto standard input for ab initio studies. So far, however, relativistic ab initio calculations have only just begun unlike disciplines such as atomic and molecular physics and chemistry. One of the most important issues restricting its development is the lack of modern relativistic nucleon-nucleon interactions. In order to promote the development of relativistic ab initio nuclear physics researches, improve our understanding of the strong interaction and compensate the deficiencies of Weinberg chiral nuclear force, our group in Beihang university together with the cooperators developed the first high precision relativistic chiral nuclear force. In this work, we briefly review the development venation and current status of the Weinberg chiral nuclear force, as well as its deficiencies. We further present a short introduction to the framework of relativistic chiral nuclear force, show its description of the scattering phase shifts as well as observables such as differential cross sections and demonstrate its advantages over Weinberg chiral nuclear force. At last we prospected its future developments and applications.
Understanding the nucleon-nucleon interaction in free space and in medium has always been one of the most important topics in nuclear physics. It is also one of the most important objectives of large scientific facilities such as HIAF and FRIB. Understanding nuclear structure, reactions, and the properties of dense stars from ab initio calculations based on nucleon degrees of freedom and microscopic nuclear forces has always been a primary goal pursued by nuclear physicists. First proposed by Nobel laureate Weinberg in 1990s and developed by joint efforts of scientists around the world, the Weinberg chiral nuclear force has now been the de facto standard input for ab initio studies. So far, however, relativistic ab initio calculations have only just begun unlike disciplines such as atomic and molecular physics and chemistry. One of the most important issues restricting its development is the lack of modern relativistic nucleon-nucleon interactions. In order to promote the development of relativistic ab initio nuclear physics researches, improve our understanding of the strong interaction and compensate the deficiencies of Weinberg chiral nuclear force, our group in Beihang university together with the cooperators developed the first high precision relativistic chiral nuclear force. In this work, we briefly review the development venation and current status of the Weinberg chiral nuclear force, as well as its deficiencies. We further present a short introduction to the framework of relativistic chiral nuclear force, show its description of the scattering phase shifts as well as observables such as differential cross sections and demonstrate its advantages over Weinberg chiral nuclear force. At last we prospected its future developments and applications.
2024, 41(1): 51-59.
doi: 10.11804/NuclPhysRev.41.2023CNPC83
Abstract:
This paper reviews two methods for studying the hadron partonic structure by quantum computing: (1) Direct calculation of parton distribution functions (PDFs) through light-cone correlators; (2) Based on QCD factorization theorem, extract PDFs from hadronic tensors which are calculated on a quantum computer. Based on the methodology of the second method and the quantum algorithm developed in reference(LI T, GUO X, LAI W K, et al. Phys Rev D, 2022, 105(11): L111502), we proposed a quantum algorithm for calculating hadronic tensors. To verify the effectiveness of our quantum algorithm, we computed the hadronic tensor of the Schwinger model and found that the results from quantum computing match those from exact diagonalization obtained by classical simulation. Finally, we briefly discuss the quantum computing resources required for calculating PDFs using the second method mentioned above.
This paper reviews two methods for studying the hadron partonic structure by quantum computing: (1) Direct calculation of parton distribution functions (PDFs) through light-cone correlators; (2) Based on QCD factorization theorem, extract PDFs from hadronic tensors which are calculated on a quantum computer. Based on the methodology of the second method and the quantum algorithm developed in reference(LI T, GUO X, LAI W K, et al. Phys Rev D, 2022, 105(11): L111502), we proposed a quantum algorithm for calculating hadronic tensors. To verify the effectiveness of our quantum algorithm, we computed the hadronic tensor of the Schwinger model and found that the results from quantum computing match those from exact diagonalization obtained by classical simulation. Finally, we briefly discuss the quantum computing resources required for calculating PDFs using the second method mentioned above.
2024, 41(1): 60-66.
doi: 10.11804/NuclPhysRev.41.2023CNPC81
Abstract:
Major national science and technology infrastructures, the High Intensity Heavy-ion Accelerator Facility (HIAF) and The China initiative Accelerator Driven System (CiADS) are under construction in Huizhou, Guangdong Province, China. HIAF, which aims to build a next-generation, world-leading high intensity heavy-ion accelerator, started construction in 2018 with a seven-year construction period and has now entered the phase of batch processing and testing, as well as on-site installation and commissioning. CiADS is proposed to be the world's first megawatt-scale accelerator-driven transmutation research facility to realize high-power coupled operation, started construction in 2021 with a construction period of six years. The construction is progressing in phases, the accelerator has started on-site installation, the high-power target has completed prototype development and the subcritical reactor is under engineering design. Building on the previous article which introduced the basics of the HIAF and CiADS projects, this paper further describes the scientific and engineering objectives, process development and civil progress, and provides an outlook on future developments.
Major national science and technology infrastructures, the High Intensity Heavy-ion Accelerator Facility (HIAF) and The China initiative Accelerator Driven System (CiADS) are under construction in Huizhou, Guangdong Province, China. HIAF, which aims to build a next-generation, world-leading high intensity heavy-ion accelerator, started construction in 2018 with a seven-year construction period and has now entered the phase of batch processing and testing, as well as on-site installation and commissioning. CiADS is proposed to be the world's first megawatt-scale accelerator-driven transmutation research facility to realize high-power coupled operation, started construction in 2021 with a construction period of six years. The construction is progressing in phases, the accelerator has started on-site installation, the high-power target has completed prototype development and the subcritical reactor is under engineering design. Building on the previous article which introduced the basics of the HIAF and CiADS projects, this paper further describes the scientific and engineering objectives, process development and civil progress, and provides an outlook on future developments.
2024, 41(1): 67-74.
doi: 10.11804/NuclPhysRev.41.2023CNPC38
Abstract:
This article introduces the construction and trial operation of Shanghai Laser Electron Gamma Source (SLEGS) beamline, one of the Shanghai Synchrotron radiation Facility (SSRF) projects II, which can carry out basic research on nuclear physics and nuclear astrophysics, and applied research, such as gamma irradiation, gamma imaging and gamma activation. The SLEGS beamline passed the process acceptance in December 2021, entered the trial operation stage in October 2022, and have open to users in September 2023. SLEGS is the first Laser Compton Slant Scattering(LCSS) beamline in the world use the continuous collision angle mode to change the energy of the gamma beam, with the best ability of energy scanning accuracy, beam intensity and efficient energy regulation. In the trial operation stage, the SLEGS beamline station focused on solving the problem of online monitoring of gamma beam energy spectrum and beam intensity, mainly completed the experimental methodology research of photo neutron cross section measurement by Flat Efficiency Detectors (FED), and carried out the expansion and research of application platforms, such as gamma imaging, gamma activation and positron source generation. With the development of inverse Compton scattering techniques, short-pulse, high-polarization, high-intensity and miniaturized laser Compton scattering light sources will be in better development opportunities in the future, and will play an important role in nuclear physics, astrophysics, particle physics, polarization physics, as well as aerospace, medical testing, energy development and other gamma source application research fields.
This article introduces the construction and trial operation of Shanghai Laser Electron Gamma Source (SLEGS) beamline, one of the Shanghai Synchrotron radiation Facility (SSRF) projects II, which can carry out basic research on nuclear physics and nuclear astrophysics, and applied research, such as gamma irradiation, gamma imaging and gamma activation. The SLEGS beamline passed the process acceptance in December 2021, entered the trial operation stage in October 2022, and have open to users in September 2023. SLEGS is the first Laser Compton Slant Scattering(LCSS) beamline in the world use the continuous collision angle mode to change the energy of the gamma beam, with the best ability of energy scanning accuracy, beam intensity and efficient energy regulation. In the trial operation stage, the SLEGS beamline station focused on solving the problem of online monitoring of gamma beam energy spectrum and beam intensity, mainly completed the experimental methodology research of photo neutron cross section measurement by Flat Efficiency Detectors (FED), and carried out the expansion and research of application platforms, such as gamma imaging, gamma activation and positron source generation. With the development of inverse Compton scattering techniques, short-pulse, high-polarization, high-intensity and miniaturized laser Compton scattering light sources will be in better development opportunities in the future, and will play an important role in nuclear physics, astrophysics, particle physics, polarization physics, as well as aerospace, medical testing, energy development and other gamma source application research fields.
2024, 41(1): 75-85.
doi: 10.11804/NuclPhysRev.41.2023CNPC56
Abstract:
With the development of radioactive-ion-beam facilities, many exotic phenomena have been discovered or predicted in the nuclei far from the $\beta$ stability line, including cluster structure, shell structure, deformed halo, and shape decoupling effects. The study of exotic nuclear phenomena is at the frontier of nuclear physics nowadays. The covariant density functional theory (CDFT) is one of the most successful microscopic models in describing the structure of nuclei in almost the whole nuclear chart. Within the framework of CDFT, toward a proper treatment of deformation and weak binding, the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) has been developed. In this contribution, we review the applications and extensions of the DRHBc theory to the study of exotic nuclei. The DRHBc theory has been used to investigate the deformed halos in B, C, Ne, Na, and Mg isotopes and the theoretical descriptions are reasonably consistent with available data. A DRHBc Mass Table Collaboration has been founded, aiming at a high precision nuclear mass table with deformation and continuum effects included, which is underway. By implementing the angular momentum projection based on the DRHBc theory, the rotational excitations of deformed halos have been investigated and it is shown that the deformed halos and shape decoupling effects also exist in the low-lying rotational excitation states of deformed halo nuclei.
With the development of radioactive-ion-beam facilities, many exotic phenomena have been discovered or predicted in the nuclei far from the $\beta$ stability line, including cluster structure, shell structure, deformed halo, and shape decoupling effects. The study of exotic nuclear phenomena is at the frontier of nuclear physics nowadays. The covariant density functional theory (CDFT) is one of the most successful microscopic models in describing the structure of nuclei in almost the whole nuclear chart. Within the framework of CDFT, toward a proper treatment of deformation and weak binding, the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) has been developed. In this contribution, we review the applications and extensions of the DRHBc theory to the study of exotic nuclei. The DRHBc theory has been used to investigate the deformed halos in B, C, Ne, Na, and Mg isotopes and the theoretical descriptions are reasonably consistent with available data. A DRHBc Mass Table Collaboration has been founded, aiming at a high precision nuclear mass table with deformation and continuum effects included, which is underway. By implementing the angular momentum projection based on the DRHBc theory, the rotational excitations of deformed halos have been investigated and it is shown that the deformed halos and shape decoupling effects also exist in the low-lying rotational excitation states of deformed halo nuclei.
2024, 41(1): 86-93.
doi: 10.11804/NuclPhysRev.41.2023CNPC80
Abstract:
Studies of nuclear exotic decay and structure around the drip line are of critical importance for understanding new laws in nuclei and developing new nuclear theories. In recent years, significant progress has been made in related research. However, there are still numerous new phenomena and mechanisms, which need further exploration. In this paper, the two-proton decay of resonant states in $^{16}\rm Ne$ is used as an example to introduce the applications of the invariant mass method in proton decay studies. With the invariant mass method, the decay energies and the corresponding momentum correlations of the ground state and the first excited state in $^{16}\rm Ne$ are determined. Comparative analysis with results obtained using the decay-in-flight method has illustrated that the invariant mass method, with its complete kinematic measurements, offers more precise results about the decay characteristics of resonant states. By simulating invariant mass spectra under the assumption of different half-lives for the ground state of $^{16}\rm Ne$, the impact of nuclear lifetime on the accuracy of the invariant mass spectrum is studied. The results indicate that the invariant mass method is effective and reliable for short-lived nuclei, while the decay-in-flight method is more suitable for long-lived nuclei.
Studies of nuclear exotic decay and structure around the drip line are of critical importance for understanding new laws in nuclei and developing new nuclear theories. In recent years, significant progress has been made in related research. However, there are still numerous new phenomena and mechanisms, which need further exploration. In this paper, the two-proton decay of resonant states in $^{16}\rm Ne$ is used as an example to introduce the applications of the invariant mass method in proton decay studies. With the invariant mass method, the decay energies and the corresponding momentum correlations of the ground state and the first excited state in $^{16}\rm Ne$ are determined. Comparative analysis with results obtained using the decay-in-flight method has illustrated that the invariant mass method, with its complete kinematic measurements, offers more precise results about the decay characteristics of resonant states. By simulating invariant mass spectra under the assumption of different half-lives for the ground state of $^{16}\rm Ne$, the impact of nuclear lifetime on the accuracy of the invariant mass spectrum is studied. The results indicate that the invariant mass method is effective and reliable for short-lived nuclei, while the decay-in-flight method is more suitable for long-lived nuclei.
2024, 41(1): 94-108.
doi: 10.11804/NuclPhysRev.41.2023CNPC82
Abstract:
Radiation imaging is an important aspect of nuclear radiation measurement. In the field of radiation safety, typical radiation imaging methods mainly include pinhole imaging, (spatial) coded aperture imaging, time-coded imaging, and Compton scattering imaging, etc, each with its own advantages, disadvantages, and applicable scenarios. Based on the accumulation of existing imaging technology methods and the experience in the development of advanced imaging equipment, this article explores three feasible schemes for the three-dimensional positioning of radiation hotspots, the application of artificial intelligence in the dynamic imaging of radiation hotspots, nuclear identification, and the intelligentization of radiation imaging platforms. It addresses the actual needs of radiation detection (imaging) that is “faster, more accurate, and covers a larger range.” In the research on the three-dimensional positioning of radiation hotspots, a four-eye stereo imaging system has achieved a distance measurement accuracy of less than 20% for radioactive sources at a distance of 100 meters in long-distance imaging scenarios. In indoor scenes, three-dimensional positioning of four radioactive sources has been achieved through three-dimensional scene modeling and radiation field construction. In the application of artificial intelligence algorithms, real-time positioning of moving radiation hotspots has been realized, capable of dynamically tracking and positioning a 14 mCi 137Cs radioactive source moving at a speed of 36 km/h at a distance of 25 meters. In the research on neural network nuclear identification algorithms, a feature-enhanced convolutional neural network based on prior energy information has been proposed, which can quickly identify nuclear substances in environments with low counts and mixed nuclear species. In the development of intelligent radiation imaging platforms, an accelerator tunnel environmental inspection robot capable of detecting radiation hotspots has been developed, and a vehicle-mounted radiation emergency monitoring platform has been created. Equipped with multiple detection terminals such as unmanned aerial vehicle (UAV) mounted, vehicle-mounted, and portable gamma cameras, it can quickly mobilize measurements in urban areas during radiation emergencies. The various intelligent radiation imaging technologies presented in this paper enable people to obtain the three-dimensional distribution and nuclear information of radioactive sources more quickly and accurately, providing advanced and efficient radiation detection technical means for radiation environmental assessment, radiation protection, nuclear emergency drills, and decision-making.
Radiation imaging is an important aspect of nuclear radiation measurement. In the field of radiation safety, typical radiation imaging methods mainly include pinhole imaging, (spatial) coded aperture imaging, time-coded imaging, and Compton scattering imaging, etc, each with its own advantages, disadvantages, and applicable scenarios. Based on the accumulation of existing imaging technology methods and the experience in the development of advanced imaging equipment, this article explores three feasible schemes for the three-dimensional positioning of radiation hotspots, the application of artificial intelligence in the dynamic imaging of radiation hotspots, nuclear identification, and the intelligentization of radiation imaging platforms. It addresses the actual needs of radiation detection (imaging) that is “faster, more accurate, and covers a larger range.” In the research on the three-dimensional positioning of radiation hotspots, a four-eye stereo imaging system has achieved a distance measurement accuracy of less than 20% for radioactive sources at a distance of 100 meters in long-distance imaging scenarios. In indoor scenes, three-dimensional positioning of four radioactive sources has been achieved through three-dimensional scene modeling and radiation field construction. In the application of artificial intelligence algorithms, real-time positioning of moving radiation hotspots has been realized, capable of dynamically tracking and positioning a 14 mCi 137Cs radioactive source moving at a speed of 36 km/h at a distance of 25 meters. In the research on neural network nuclear identification algorithms, a feature-enhanced convolutional neural network based on prior energy information has been proposed, which can quickly identify nuclear substances in environments with low counts and mixed nuclear species. In the development of intelligent radiation imaging platforms, an accelerator tunnel environmental inspection robot capable of detecting radiation hotspots has been developed, and a vehicle-mounted radiation emergency monitoring platform has been created. Equipped with multiple detection terminals such as unmanned aerial vehicle (UAV) mounted, vehicle-mounted, and portable gamma cameras, it can quickly mobilize measurements in urban areas during radiation emergencies. The various intelligent radiation imaging technologies presented in this paper enable people to obtain the three-dimensional distribution and nuclear information of radioactive sources more quickly and accurately, providing advanced and efficient radiation detection technical means for radiation environmental assessment, radiation protection, nuclear emergency drills, and decision-making.
2024, 41(1): 109-116.
doi: 10.11804/NuclPhysRev.41.2023CNPC74
Abstract:
The transition of strong-interaction matter from the hadronic phase to the quark-gluon plasma phase is a rapid crossover but not a true phase transition in nature. The true phase transition of strong-interaction matter is expected to exist only in certain limits, e.g. chiral limit of massless quarks and etc. In this contribution to CNPC2023 Special Issue we present our recent studies on the true phase transition of strong-interaction matter in the chiral limit of massless quarks as well as its microscopic origin. The study is based on (2+1)-flavor lattice QCD simulations using highly improved staggered fermions, with pion masses ranging from 160 MeV down to 55 MeV. Utilizing a newly proposed method to compute the quark mass derivatives of the Dirac eigenvalue spectrum on the lattice, it is found that the axial U(1) anomaly is still manifested at 1.6 $T_{\rm c}$, with a microscopic origin consistent with the dilute instanton gas approximation. Furthermore, based on lattice QCD results and a generalized Banks-Casher relation, it is found that the macroscopic singularity of the chiral phase transition is encoded in the correlation of the Dirac eigenvalue spectrum. Future research directions along these findings are also discussed, including the investigation of the temperature range between $T_{\rm c}$ and 1.6 $T_{\rm c}$ to understand the breakdown of the dilute instanton gas approximation and its connection to the chiral phase transition.
The transition of strong-interaction matter from the hadronic phase to the quark-gluon plasma phase is a rapid crossover but not a true phase transition in nature. The true phase transition of strong-interaction matter is expected to exist only in certain limits, e.g. chiral limit of massless quarks and etc. In this contribution to CNPC2023 Special Issue we present our recent studies on the true phase transition of strong-interaction matter in the chiral limit of massless quarks as well as its microscopic origin. The study is based on (2+1)-flavor lattice QCD simulations using highly improved staggered fermions, with pion masses ranging from 160 MeV down to 55 MeV. Utilizing a newly proposed method to compute the quark mass derivatives of the Dirac eigenvalue spectrum on the lattice, it is found that the axial U(1) anomaly is still manifested at 1.6 $T_{\rm c}$, with a microscopic origin consistent with the dilute instanton gas approximation. Furthermore, based on lattice QCD results and a generalized Banks-Casher relation, it is found that the macroscopic singularity of the chiral phase transition is encoded in the correlation of the Dirac eigenvalue spectrum. Future research directions along these findings are also discussed, including the investigation of the temperature range between $T_{\rm c}$ and 1.6 $T_{\rm c}$ to understand the breakdown of the dilute instanton gas approximation and its connection to the chiral phase transition.
2024, 41(1): 117-126.
doi: 10.11804/NuclPhysRev.41.2023CNPC65
Abstract:
The study of nuclear isoscalar giant monopole resonance (ISGMR) is an important way to constrain nuclear incompressibility coefficient $K_\infty$, which provides important information for the understanding of nuclear astrophysics phenomena. At present, there is a serious discrepancy in the unified descriptions of the ISGMR in Pb and Sn isotopes, i.e., the so called "why is the equation of state for tin so soft?", which prevents us from the accurate determination of $K_\infty$. In this paper, we introduce the quasiparticle random phase approximation (QRPA) theory, which is commonly used in the study of nuclear giant resonances, and also the self-consistent quasiparticle-vibration coupling (QPVC) theory based on the QRPA. The researches for the current issue within QRPA and QRPA+QPVC theories are reviewed, especially for the important role of the QPVC effects in achieving a unified description of ISGMR: a unified descriptions of ISGMR in Sn and Pb can be achieved with the QPVC effects, the problem "why is the equation of state for tin so soft?" can be solved, and the incompressibility coefficient $K_\infty$ is constrained. Besides, based on the self-consistent QPVC theory, we further studied the electric monopole excitation strength disctributions in the neutron-rich Sn isotopes134, 140Sn.
The study of nuclear isoscalar giant monopole resonance (ISGMR) is an important way to constrain nuclear incompressibility coefficient $K_\infty$, which provides important information for the understanding of nuclear astrophysics phenomena. At present, there is a serious discrepancy in the unified descriptions of the ISGMR in Pb and Sn isotopes, i.e., the so called "why is the equation of state for tin so soft?", which prevents us from the accurate determination of $K_\infty$. In this paper, we introduce the quasiparticle random phase approximation (QRPA) theory, which is commonly used in the study of nuclear giant resonances, and also the self-consistent quasiparticle-vibration coupling (QPVC) theory based on the QRPA. The researches for the current issue within QRPA and QRPA+QPVC theories are reviewed, especially for the important role of the QPVC effects in achieving a unified description of ISGMR: a unified descriptions of ISGMR in Sn and Pb can be achieved with the QPVC effects, the problem "why is the equation of state for tin so soft?" can be solved, and the incompressibility coefficient $K_\infty$ is constrained. Besides, based on the self-consistent QPVC theory, we further studied the electric monopole excitation strength disctributions in the neutron-rich Sn isotopes134, 140Sn.
2024, 41(1): 127-134.
doi: 10.11804/NuclPhysRev.41.2023CNPC84
Abstract:
This study systematically investigates the impacts of uncertainties in the form and the strength of the pairing force on observables related to nuclear fission, taking the neutron-induced fission of 239Pu as an example, thereby revealing the role of pairing in the fission process. The energy density functional theory (DFT) based on the Skyrme force was employed to calculate the potential energy surface in the two-dimensional deformation space of 240Pu, using volume, surface, and mixed pairing forces within the Hartree-Fock-Bogoliubov (HFB) approximation. And we also test the effects of varying pairing strengths for the mixed pairing force. Subsequently, based on the DFT calculations, the fission dynamics of 240Pu were further studied using the Time-Dependent Generator Coordinate Method (TDGCM) plus the Gaussian Overlap Approximation (GOA). By analyzing the influence of varying the types or the strength of the pairing force on fission related properties, we found that variation in the pairing strength significantly affect both small and large deformation regions. However, alterations in pairing force type primarily cause notable differences in the large deformation region. The configurations at large deformation in the nucleus have significant impacts on the fission dynamics. Our results show that there are explicit differences in the configurations at large deformations obtained by different types of pairing force, so the choice of pairing force is very important for the fission description. The mixed-type of pairing force gives the best results in the calculation of fission dynamics.
This study systematically investigates the impacts of uncertainties in the form and the strength of the pairing force on observables related to nuclear fission, taking the neutron-induced fission of 239Pu as an example, thereby revealing the role of pairing in the fission process. The energy density functional theory (DFT) based on the Skyrme force was employed to calculate the potential energy surface in the two-dimensional deformation space of 240Pu, using volume, surface, and mixed pairing forces within the Hartree-Fock-Bogoliubov (HFB) approximation. And we also test the effects of varying pairing strengths for the mixed pairing force. Subsequently, based on the DFT calculations, the fission dynamics of 240Pu were further studied using the Time-Dependent Generator Coordinate Method (TDGCM) plus the Gaussian Overlap Approximation (GOA). By analyzing the influence of varying the types or the strength of the pairing force on fission related properties, we found that variation in the pairing strength significantly affect both small and large deformation regions. However, alterations in pairing force type primarily cause notable differences in the large deformation region. The configurations at large deformation in the nucleus have significant impacts on the fission dynamics. Our results show that there are explicit differences in the configurations at large deformations obtained by different types of pairing force, so the choice of pairing force is very important for the fission description. The mixed-type of pairing force gives the best results in the calculation of fission dynamics.
2024, 41(1): 135-140.
doi: 10.11804/NuclPhysRev.41.2023CNPC63
Abstract:
Multinucleon transfer reactions involving heavy actinide projectile and target nuclei hold significant potential as a groundbreaking method to synthesize neutron-rich superheavy nuclei. Constructing a Prototype Spectrometer for Neutron-rich Superheavy Nuclei is highly desirable to establish the technical, methodological, and device foundation to explore the stability island in superheavy nuclei and to study the mechanism of multinucleon transfer reactions. The gas cell of the Prototype Spectrometer for Neutron-rich Superheavy Nuclei requires a continuous supply of high-purity helium gas to stop the energetic radioactive reaction products and to extract the energy-reduced ions to the subsequent experimental setup. The paper focuses on a newly developed Gas Cell Cryogenic Purification System operating at Prototype Spectrometer for Neutron-rich Superheavy Nuclei. This system is designed to provide recyclable and high-purity helium for the gas cell. With a series of tests, the cryogenic purification system has been proven to be able to purify the 99% helium gas to 99.999% or higher, fulfilling the requirements of the gas cell when used in conjunction with the chemical purification system.
Multinucleon transfer reactions involving heavy actinide projectile and target nuclei hold significant potential as a groundbreaking method to synthesize neutron-rich superheavy nuclei. Constructing a Prototype Spectrometer for Neutron-rich Superheavy Nuclei is highly desirable to establish the technical, methodological, and device foundation to explore the stability island in superheavy nuclei and to study the mechanism of multinucleon transfer reactions. The gas cell of the Prototype Spectrometer for Neutron-rich Superheavy Nuclei requires a continuous supply of high-purity helium gas to stop the energetic radioactive reaction products and to extract the energy-reduced ions to the subsequent experimental setup. The paper focuses on a newly developed Gas Cell Cryogenic Purification System operating at Prototype Spectrometer for Neutron-rich Superheavy Nuclei. This system is designed to provide recyclable and high-purity helium for the gas cell. With a series of tests, the cryogenic purification system has been proven to be able to purify the 99% helium gas to 99.999% or higher, fulfilling the requirements of the gas cell when used in conjunction with the chemical purification system.
2024, 41(1): 141-147.
doi: 10.11804/NuclPhysRev.41.2023CNPC01
Abstract:
Reaction dynamics, especially the breakup mechanisms, induced by proton drip-line nuclei at energies around the Coulomb barrier, is one of the most popular topics in nuclear physics. In order to further investigate the reaction mechanisms of proton drip-line nuclei, we performed the complete-kinematics measurements of 8B+120Sn and 17F+58Ni at CRIB, University of Tokyo. This paper summarizes our research findings and unveils for the first time the fusion cross-section results in the 8B+120Sn measurement. Two detector arrays, i.e., the silicon telescope array of STARE and the ionization chamber array of MITA, were designed respectively for the measurements of 8B and 17F. Reaction products were completely identified with the help of these two arrays. For the 8B+120Sn system, the coincident measurement of the breakup fragments was achieved for the first time. The correlations between the breakup fragments reveal that the prompt breakup occurring on the outgoing trajectory dominates the breakup dynamics of 8B. For 17F+58Ni, the complete reaction channel information, such as quasi-elastic scattering, breakup and total fusion, was derived for the first time. An enhancement of the fusion cross section of 17F+58Ni was observed at the energy below the Coulomb barrier. Theoretical calculations indicate that this phenomenon is mainly due to the coupling to the continuum states. Moreover, different direct reaction dynamics were found in 8B and 17F systems, suggesting the influence of proton-halo structure on the reaction dynamics.
Reaction dynamics, especially the breakup mechanisms, induced by proton drip-line nuclei at energies around the Coulomb barrier, is one of the most popular topics in nuclear physics. In order to further investigate the reaction mechanisms of proton drip-line nuclei, we performed the complete-kinematics measurements of 8B+120Sn and 17F+58Ni at CRIB, University of Tokyo. This paper summarizes our research findings and unveils for the first time the fusion cross-section results in the 8B+120Sn measurement. Two detector arrays, i.e., the silicon telescope array of STARE and the ionization chamber array of MITA, were designed respectively for the measurements of 8B and 17F. Reaction products were completely identified with the help of these two arrays. For the 8B+120Sn system, the coincident measurement of the breakup fragments was achieved for the first time. The correlations between the breakup fragments reveal that the prompt breakup occurring on the outgoing trajectory dominates the breakup dynamics of 8B. For 17F+58Ni, the complete reaction channel information, such as quasi-elastic scattering, breakup and total fusion, was derived for the first time. An enhancement of the fusion cross section of 17F+58Ni was observed at the energy below the Coulomb barrier. Theoretical calculations indicate that this phenomenon is mainly due to the coupling to the continuum states. Moreover, different direct reaction dynamics were found in 8B and 17F systems, suggesting the influence of proton-halo structure on the reaction dynamics.
2024, 41(1): 148-155.
doi: 10.11804/NuclPhysRev.41.2023CNPC87
Abstract:
Using a microscopic four-body cluster model, we investigate the spectral properties and structural configurations of the $ \rm {}^{10}Be $ nucleus. We calculate physical quantities such as the root-mean-squared (r.m.s.) radii and electromagnetic transition strengths. The theoretical results for the energies and certain electromagnetic transition strengths of the low-lying states show good agreement with experimental data. In particular, the enhancement of the r.m.s. radius and isoscalar monopole transition strength of the $ 0_3^+ $ state indicates a well-developed cluster structure. We obtained three $ 1^- $ states in $ E_{\rm x}< 15 $ MeV that show remarkable dipole transition strengths, suggesting that the $ 1^- $ states may have cluster structure. Using the obtained wave functions, we calculate the reduced-width amplitudes (RWAs) to investigate the $ ^6\text{He}+\alpha $ and $ ^9\text{Be}+ {\rm{n}} $ two-body cluster structures in 10Be. The results suggest that the low-lying states show the two-body $ {}^{6}\text{He}+\alpha $ and $ \rm {}^{9}Be+ {\rm{n}} $ configuration, with the $ ^6\text{He}+\alpha $ components of the two-body structure diminishing as the energy increases, which due to the breakup of $ \rm{}^6He $ and $ \rm{}^9Be $ at higher excitation energies. Moreover, a few states above the $ \alpha+\alpha+ {\rm{n}}+ {\rm{n}} $ threshold still exhibit significant $ ^9\text{Be}+ {\rm{n}} $ components.
Using a microscopic four-body cluster model, we investigate the spectral properties and structural configurations of the $ \rm {}^{10}Be $ nucleus. We calculate physical quantities such as the root-mean-squared (r.m.s.) radii and electromagnetic transition strengths. The theoretical results for the energies and certain electromagnetic transition strengths of the low-lying states show good agreement with experimental data. In particular, the enhancement of the r.m.s. radius and isoscalar monopole transition strength of the $ 0_3^+ $ state indicates a well-developed cluster structure. We obtained three $ 1^- $ states in $ E_{\rm x}< 15 $ MeV that show remarkable dipole transition strengths, suggesting that the $ 1^- $ states may have cluster structure. Using the obtained wave functions, we calculate the reduced-width amplitudes (RWAs) to investigate the $ ^6\text{He}+\alpha $ and $ ^9\text{Be}+ {\rm{n}} $ two-body cluster structures in 10Be. The results suggest that the low-lying states show the two-body $ {}^{6}\text{He}+\alpha $ and $ \rm {}^{9}Be+ {\rm{n}} $ configuration, with the $ ^6\text{He}+\alpha $ components of the two-body structure diminishing as the energy increases, which due to the breakup of $ \rm{}^6He $ and $ \rm{}^9Be $ at higher excitation energies. Moreover, a few states above the $ \alpha+\alpha+ {\rm{n}}+ {\rm{n}} $ threshold still exhibit significant $ ^9\text{Be}+ {\rm{n}} $ components.
2024, 41(1): 156-162.
doi: 10.11804/NuclPhysRev.41.2023CNPC73
Abstract:
Numerous candidates for exotic hadrons have been detected experimentally in the past two decades, predominantly near the threshold of a pair of hadrons. This study aims to investigate the overall behavior of near-threshold line shapes in invariant mass distributions. It is noteworthy that the threshold cusp might manifest as a peak only in channels with attractive interaction. The assertion is made that there should be near-threshold structures for any heavy-quark and heavy-antiquark hadron pairs exhibiting attractive interaction at the threshold, as observed in the invariant mass distribution of heavy quarkonium and light hadrons that couple to the open-flavor hadron pair. Furthermore, we have conducted an analysis of potential hadronic molecules comprising pairs of heavy hadrons, utilizing the Bethe-Salpeter equation with constant interactions derived from the one-boson-exchange model. Observed candidates for these hadronic molecules are in good agreement with our predicted spectrum.
Numerous candidates for exotic hadrons have been detected experimentally in the past two decades, predominantly near the threshold of a pair of hadrons. This study aims to investigate the overall behavior of near-threshold line shapes in invariant mass distributions. It is noteworthy that the threshold cusp might manifest as a peak only in channels with attractive interaction. The assertion is made that there should be near-threshold structures for any heavy-quark and heavy-antiquark hadron pairs exhibiting attractive interaction at the threshold, as observed in the invariant mass distribution of heavy quarkonium and light hadrons that couple to the open-flavor hadron pair. Furthermore, we have conducted an analysis of potential hadronic molecules comprising pairs of heavy hadrons, utilizing the Bethe-Salpeter equation with constant interactions derived from the one-boson-exchange model. Observed candidates for these hadronic molecules are in good agreement with our predicted spectrum.
2024, 41(1): 163-171.
doi: 10.11804/NuclPhysRev.41.2023CNPC79
Abstract:
Experimental studies on the spontaneous nucleon emission have enabled the exploration of new isotopes beyond the drip line, as well as revealing their unique structural and decay characteristics. Furthermore, such studies are of critical importance for exploring the limits of nuclear stability and understanding the nucleon-nucleon interactions under extreme conditions of isospin asymmetry. This paper introduces our experimental study on the four-proton decay of $^{18}{\rm{Mg}}$, a new magnesium isotope beyond the proton drip line. Firstly the radioactive nuclear beamline and detector appratus are introduced, and the results of the particle identification of beam particles and decay fragments are presented. Then the scintillating fiber array is mainly introduced together with its data analysis method. With its performance of detection efficiency and position resolution, this array has been proven by simulation to be very necessary for improving the energy resolution of the invariant mass spectrum. Finally, with the five-body coincidence measurement of $^{14}{\rm{O}}+4{\rm{p}}$, the decay energy spectrum of $^{18}{\rm{Mg}}$ was constructed using the invariant mass method. The experimental results can be relatively well described by the Gamow Shell Model, demonstrating the significant impact of continuum coupling effect on the structure of nuclei beyond the drip line. The measured $2^+_1$ excitation energy in $^{18}{\rm{Mg}}$ is higher than that in the traditional magic nucleus $^{20}{\rm{Mg}}$, which suggests that a possible demise of the $N = 8$ shell closure or some exotic nuclear structure effect may occur in this extremely proton-rich Mg isotope.
Experimental studies on the spontaneous nucleon emission have enabled the exploration of new isotopes beyond the drip line, as well as revealing their unique structural and decay characteristics. Furthermore, such studies are of critical importance for exploring the limits of nuclear stability and understanding the nucleon-nucleon interactions under extreme conditions of isospin asymmetry. This paper introduces our experimental study on the four-proton decay of $^{18}{\rm{Mg}}$, a new magnesium isotope beyond the proton drip line. Firstly the radioactive nuclear beamline and detector appratus are introduced, and the results of the particle identification of beam particles and decay fragments are presented. Then the scintillating fiber array is mainly introduced together with its data analysis method. With its performance of detection efficiency and position resolution, this array has been proven by simulation to be very necessary for improving the energy resolution of the invariant mass spectrum. Finally, with the five-body coincidence measurement of $^{14}{\rm{O}}+4{\rm{p}}$, the decay energy spectrum of $^{18}{\rm{Mg}}$ was constructed using the invariant mass method. The experimental results can be relatively well described by the Gamow Shell Model, demonstrating the significant impact of continuum coupling effect on the structure of nuclei beyond the drip line. The measured $2^+_1$ excitation energy in $^{18}{\rm{Mg}}$ is higher than that in the traditional magic nucleus $^{20}{\rm{Mg}}$, which suggests that a possible demise of the $N = 8$ shell closure or some exotic nuclear structure effect may occur in this extremely proton-rich Mg isotope.
2024, 41(1): 172-177.
doi: 10.11804/NuclPhysRev.41.2023CNPC77
Abstract:
With recent years of development, Nuclear Lattice Effective Field Theory (NLEFT) is becoming a powerful and high-fidelity ab initio method. It takes advantage of the chiral effective field theory and quantum Monte Carlo on lattice and can build nuclear forces and solve quantum many-body problems in the same framework. The newly developed wave function matching method and perturbative quantum Monte Carlo method pave the way to avoid the "sign problem". In this work, we implement all these new techniques along with the two-point correlation function to measure the charge radii on lattice. Benchmark calculations show our method is solid and full N3LO calculation can well reproduce the experiment data of 4He, 12C and 16O.
With recent years of development, Nuclear Lattice Effective Field Theory (NLEFT) is becoming a powerful and high-fidelity ab initio method. It takes advantage of the chiral effective field theory and quantum Monte Carlo on lattice and can build nuclear forces and solve quantum many-body problems in the same framework. The newly developed wave function matching method and perturbative quantum Monte Carlo method pave the way to avoid the "sign problem". In this work, we implement all these new techniques along with the two-point correlation function to measure the charge radii on lattice. Benchmark calculations show our method is solid and full N3LO calculation can well reproduce the experiment data of 4He, 12C and 16O.
2024, 41(1): 178-183.
doi: 10.11804/NuclPhysRev.41.2023CNPC40
Abstract:
By including octupole correlations in the Nilsson potential, the ground-state rotational bands in the reflection-asymmetric (RA) nuclei are investigated by using the cranked shell model (CSM) with the monopole and quadrupole pairing correlations treated by a particle-number-conserving (PNC) method. The experimental kinematic moments of inertia (MoIs) for alternating-parity bands in the even-even nuclei $^{236, \, 238} {\rm{U}}$ and $^{238, \, 240} {\rm{Pu}}$, as well as parity-doublet bands in the odd-$ A $ nuclei $ ^{237} {\rm{U}}$ and $ ^{239} {\rm{Pu}}$ are reproduced well by the PNC-CSM calculations. The higher $ J^{(1)} $ for the intrinsic $s = -i$ bands in $ ^{237} {\rm{U}}$ and $ ^{239} {\rm{Pu}}$, compared with the $s = +1$ bands in the neighboring even-even nuclei $^{236, \, 238} {\rm{U}}$ and $^{238, \, 240} {\rm{Pu}}$, can be attributed to the pairing gap reduction due to the Pauli blocking effect. The gradual increase of $ J^{(1)} $ versus rotational frequency can be explained by the pairing gap reduction due to the rotation. The MoIs of reflection-asymmetric nuclei are higher than those of reflection-symmetric (RS) nuclei at low rotational frequency. Moreover, the inclusion of a larger octupole deformation $ \varepsilon_3^{} $ in the RA nuclei results in more significant pairing gap reduction compared with the RS nuclei.
By including octupole correlations in the Nilsson potential, the ground-state rotational bands in the reflection-asymmetric (RA) nuclei are investigated by using the cranked shell model (CSM) with the monopole and quadrupole pairing correlations treated by a particle-number-conserving (PNC) method. The experimental kinematic moments of inertia (MoIs) for alternating-parity bands in the even-even nuclei $^{236, \, 238} {\rm{U}}$ and $^{238, \, 240} {\rm{Pu}}$, as well as parity-doublet bands in the odd-$ A $ nuclei $ ^{237} {\rm{U}}$ and $ ^{239} {\rm{Pu}}$ are reproduced well by the PNC-CSM calculations. The higher $ J^{(1)} $ for the intrinsic $s = -i$ bands in $ ^{237} {\rm{U}}$ and $ ^{239} {\rm{Pu}}$, compared with the $s = +1$ bands in the neighboring even-even nuclei $^{236, \, 238} {\rm{U}}$ and $^{238, \, 240} {\rm{Pu}}$, can be attributed to the pairing gap reduction due to the Pauli blocking effect. The gradual increase of $ J^{(1)} $ versus rotational frequency can be explained by the pairing gap reduction due to the rotation. The MoIs of reflection-asymmetric nuclei are higher than those of reflection-symmetric (RS) nuclei at low rotational frequency. Moreover, the inclusion of a larger octupole deformation $ \varepsilon_3^{} $ in the RA nuclei results in more significant pairing gap reduction compared with the RS nuclei.
2024, 41(1): 184-190.
doi: 10.11804/NuclPhysRev.41.2023CNPC68
Abstract:
A systematic comparison of the negative parity yrast states' energy level structures indicates a level inversion between the$9/2^-$ and the $11/2^-$ in 55Co, and suggests that 53Co and 57Co might exhibit strong collective effects. Shell model calculations based on the GXPF1A effective interaction accurately reproduce yrast state halo state energy levels of these nuclei, as well as the corresponding experimental magnetic moments and electric quadrupole moments. The shell model results show that the dominant component of proton configuration for the ground state $7/2^-$ in 53−65Co is $\pi\left(1f_{7/2}\right)^7$. The excited states $9/2^-$ and $11/2^-$ in 55Co involve a competition between $1f_{7/2}$ proton excitation and $1f_{7/2}$ neutron excitation, leading to a possible level inversion between the these states. Moreover, by using the Constrained Hartree-Fock (CHF) method to study the quadrupole deformation characteristics of 53Co, 55Co and 57Co, and combining the average occupancy numbers and configurations obtained from shell model calculations, the reasons for higher the excited state energies of 55Co compared to other Co isotopes were analyzed.
A systematic comparison of the negative parity yrast states' energy level structures indicates a level inversion between the$9/2^-$ and the $11/2^-$ in 55Co, and suggests that 53Co and 57Co might exhibit strong collective effects. Shell model calculations based on the GXPF1A effective interaction accurately reproduce yrast state halo state energy levels of these nuclei, as well as the corresponding experimental magnetic moments and electric quadrupole moments. The shell model results show that the dominant component of proton configuration for the ground state $7/2^-$ in 53−65Co is $\pi\left(1f_{7/2}\right)^7$. The excited states $9/2^-$ and $11/2^-$ in 55Co involve a competition between $1f_{7/2}$ proton excitation and $1f_{7/2}$ neutron excitation, leading to a possible level inversion between the these states. Moreover, by using the Constrained Hartree-Fock (CHF) method to study the quadrupole deformation characteristics of 53Co, 55Co and 57Co, and combining the average occupancy numbers and configurations obtained from shell model calculations, the reasons for higher the excited state energies of 55Co compared to other Co isotopes were analyzed.
2024, 41(1): 191-199.
doi: 10.11804/NuclPhysRev.41.2023CNPC28
Abstract:
Since the discovery of the halo nucleus 11Li in 1985, halo phenomena in exotic nuclei have always been an important frontier in nuclear physics research. The relativistic density functional theory has achieved great success in the study of halo nuclei, e.g., the self-consistent description of halo nucleus 11Li and the microscopic prediction of deformed halo nuclei. This paper introduces some recent progresses based on the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) and the triaxial relativistic Hartree-Bogoliubov theory in continuum (TRHBc). A microscopic and self-consistent description of the deformed halo nucleus 37Mg, including its small one-neutron separation energy, large root-mean-square radius, diffuse density distribution, and p-wave components for the halo neutron, has been achieved by the DRHBc theory. The DRHBc theory has also predicted a deformed neutron halo and the collapse of the $N = 28 $ shell closure in the recently discovered isotope 39Na. The TRHBc theory has been newly developed and applied to the aluminum isotopic chain. The heaviest odd-odd 42Al has been predicted as a triaxial halo nucleus with a novel shape decoupling between its core and halo at the triaxial level.
Since the discovery of the halo nucleus 11Li in 1985, halo phenomena in exotic nuclei have always been an important frontier in nuclear physics research. The relativistic density functional theory has achieved great success in the study of halo nuclei, e.g., the self-consistent description of halo nucleus 11Li and the microscopic prediction of deformed halo nuclei. This paper introduces some recent progresses based on the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) and the triaxial relativistic Hartree-Bogoliubov theory in continuum (TRHBc). A microscopic and self-consistent description of the deformed halo nucleus 37Mg, including its small one-neutron separation energy, large root-mean-square radius, diffuse density distribution, and p-wave components for the halo neutron, has been achieved by the DRHBc theory. The DRHBc theory has also predicted a deformed neutron halo and the collapse of the $N = 28 $ shell closure in the recently discovered isotope 39Na. The TRHBc theory has been newly developed and applied to the aluminum isotopic chain. The heaviest odd-odd 42Al has been predicted as a triaxial halo nucleus with a novel shape decoupling between its core and halo at the triaxial level.
2024, 41(1): 200-206.
doi: 10.11804/NuclPhysRev.41.2023CNPC04
Abstract:
The recent progresses on the wobbling motion are briefly introduced. So far 17 wobbling candidates have been reported in odd-A and even-even nuclei that spread over A≈100, 130, 160 and 190 mass regions. The two-quasiparticle configuration wobbling in 130Ba and the wobbling motion in a triaxial rotor are taken as examples in this paper to show the wobbling motion in even-even nuclei. For the 130Ba, the wobbling are investigated based on the combination of the covariant density functional theory (CDFT) and the particle rotor model (PRM). The CDFT provides crucial information on the configuration and deformation parameters of observed bands, serving as input for PRM calculations. The corresponding experimental energy spectra and electromagnetic transition probabilities are reproduced. An analysis of the angular momentum geometry reveals the enhanced stability of transverse wobbling of a two-quasiparticle configuration compared to a single-quasiparticle one. For the triaxial rotor, the time evolution of wobbling motion is explored through the solution of Euler equations. This investigation yields valuable insights into the evolution of orientation angles ($\phi $ and $\theta $) and angular momentum components. Notably, the study reveals that low-energy states of a triaxial rotor predominantly exhibit wobbling motion around the intermediate axis. Moreover, an increase in excitation energy corresponds to a prolonged period of intermediate axis wobbling motion. Conversely, a contrasting trend is observed in the case of long axis wobbling, where an increase in excitation energy leads to a decrease in the wobbling period.
The recent progresses on the wobbling motion are briefly introduced. So far 17 wobbling candidates have been reported in odd-A and even-even nuclei that spread over A≈100, 130, 160 and 190 mass regions. The two-quasiparticle configuration wobbling in 130Ba and the wobbling motion in a triaxial rotor are taken as examples in this paper to show the wobbling motion in even-even nuclei. For the 130Ba, the wobbling are investigated based on the combination of the covariant density functional theory (CDFT) and the particle rotor model (PRM). The CDFT provides crucial information on the configuration and deformation parameters of observed bands, serving as input for PRM calculations. The corresponding experimental energy spectra and electromagnetic transition probabilities are reproduced. An analysis of the angular momentum geometry reveals the enhanced stability of transverse wobbling of a two-quasiparticle configuration compared to a single-quasiparticle one. For the triaxial rotor, the time evolution of wobbling motion is explored through the solution of Euler equations. This investigation yields valuable insights into the evolution of orientation angles ($\phi $ and $\theta $) and angular momentum components. Notably, the study reveals that low-energy states of a triaxial rotor predominantly exhibit wobbling motion around the intermediate axis. Moreover, an increase in excitation energy corresponds to a prolonged period of intermediate axis wobbling motion. Conversely, a contrasting trend is observed in the case of long axis wobbling, where an increase in excitation energy leads to a decrease in the wobbling period.
2024, 41(1): 207-213.
doi: 10.11804/NuclPhysRev.41.2023CNPC26
Abstract:
The research in hypernuclear physics provides crucial information for uncovering the characteristics of baryon-baryon interactions in the nuclear medium and understanding the internal structure of atomic nuclei and neutron stars. Based on the density-dependent relativistic Hartree-Fock (RHF) theory, the $\Lambda \rm{N}$ effective interaction in the model is obtained by fitting experimental data of hyperon separation energies for single-$\Lambda$ hypernuclei. The inclusion of the Fock term alters the dynamic equilibrium of the effective nuclear force in the hyperon channel, resulting in a meson-hyperon coupling strength that differs from the relativistic mean-field model and influences the description of hyperon spin-orbit splitting. Considering the uncertainty in the values of the effective nuclear force within the model, further research is conducted to explore the dependence of hypernuclear bulk and single-particle properties on the hyperon coupling strength, aiming to identify possible ways to constrain its range of values. Taking the $^{16}_{\Lambda}\rm{O}$ hypernucleus as an example, the effects of the nuclear medium and Fock terms are systematically analyzed by adjusting the hyperon coupling strength in the isoscalar channel within the hypernuclear energy functional. The results suggest a possible linear relationship between the ratio of hyperon coupling strength and quantities such as hyperon spin-orbit splitting, Dirac effective mass, and hypernuclear characteristic radius. Therefore, by constraining these quantities through experimental or theoretical means, it is possible to impose stronger limitations on the effective nuclear force associated with hyperons in the nuclear medium.
The research in hypernuclear physics provides crucial information for uncovering the characteristics of baryon-baryon interactions in the nuclear medium and understanding the internal structure of atomic nuclei and neutron stars. Based on the density-dependent relativistic Hartree-Fock (RHF) theory, the $\Lambda \rm{N}$ effective interaction in the model is obtained by fitting experimental data of hyperon separation energies for single-$\Lambda$ hypernuclei. The inclusion of the Fock term alters the dynamic equilibrium of the effective nuclear force in the hyperon channel, resulting in a meson-hyperon coupling strength that differs from the relativistic mean-field model and influences the description of hyperon spin-orbit splitting. Considering the uncertainty in the values of the effective nuclear force within the model, further research is conducted to explore the dependence of hypernuclear bulk and single-particle properties on the hyperon coupling strength, aiming to identify possible ways to constrain its range of values. Taking the $^{16}_{\Lambda}\rm{O}$ hypernucleus as an example, the effects of the nuclear medium and Fock terms are systematically analyzed by adjusting the hyperon coupling strength in the isoscalar channel within the hypernuclear energy functional. The results suggest a possible linear relationship between the ratio of hyperon coupling strength and quantities such as hyperon spin-orbit splitting, Dirac effective mass, and hypernuclear characteristic radius. Therefore, by constraining these quantities through experimental or theoretical means, it is possible to impose stronger limitations on the effective nuclear force associated with hyperons in the nuclear medium.
2024, 41(1): 214-220.
doi: 10.11804/NuclPhysRev.41.2023CNPC50
Abstract:
The collective excited states are macroscopically described as the nuclear resonances in coordinate, spin, and isospin spaces. Researching these excited states may acquire the properties of nuclear structure and the information of nucleon-nucleon interaction inside nucleus. In addition, it may also provide important input for nuclear astrophysics. The self-consistent Second Random Approximation (SRPA) theory based on Skyrme density functional was applied to research these collective excited states, including normal parity 0+, 2+, 3− sates, and charge-exchange Gamow-Teller (GT) transition. In addition, the effects of tensor force under the two particle-two hole configurations are discussed primarily. And the research points out that it may produce low-energy normal transition states or enhance their transition strengths. Moreover, the including of tensor force is helpful for the systematical describing of the strength and excitation energy of GT giant resonances of a series of closed-shell nuclei, and the β decay half-lives of closed-shell or quasi closed-shell nuclei.
The collective excited states are macroscopically described as the nuclear resonances in coordinate, spin, and isospin spaces. Researching these excited states may acquire the properties of nuclear structure and the information of nucleon-nucleon interaction inside nucleus. In addition, it may also provide important input for nuclear astrophysics. The self-consistent Second Random Approximation (SRPA) theory based on Skyrme density functional was applied to research these collective excited states, including normal parity 0+, 2+, 3− sates, and charge-exchange Gamow-Teller (GT) transition. In addition, the effects of tensor force under the two particle-two hole configurations are discussed primarily. And the research points out that it may produce low-energy normal transition states or enhance their transition strengths. Moreover, the including of tensor force is helpful for the systematical describing of the strength and excitation energy of GT giant resonances of a series of closed-shell nuclei, and the β decay half-lives of closed-shell or quasi closed-shell nuclei.
2024, 41(1): 221-225.
doi: 10.11804/NuclPhysRev.41.2023CNPC11
Abstract:
Based on the group-algebra theory, we illustrate how to build the quadrupole-quadrupole dynamics for the identical fermion and boson systems within the s, d single-particle orbits, by which the influence of identity principle on the many-body dynamical structures of nuclei is discussed. The results indicate that the dimension of low-spin states in the identical fermion system with a given number of particle is much larger than the corresponding situation in the identical boson system, which means that the former can involve a richer rotational structure than the latter under similar conditions. The present analysis provides an example for analyzing nuclear structural model using the SU(3) group-algebra theory.
Based on the group-algebra theory, we illustrate how to build the quadrupole-quadrupole dynamics for the identical fermion and boson systems within the s, d single-particle orbits, by which the influence of identity principle on the many-body dynamical structures of nuclei is discussed. The results indicate that the dimension of low-spin states in the identical fermion system with a given number of particle is much larger than the corresponding situation in the identical boson system, which means that the former can involve a richer rotational structure than the latter under similar conditions. The present analysis provides an example for analyzing nuclear structural model using the SU(3) group-algebra theory.
2024, 41(1): 226-232.
doi: 10.11804/NuclPhysRev.41.2023CNPC54
Abstract:
The non-collective rotational behavior of the yrast band is robustness for nuclei in the presence of random interactions, where the mathematical expectation of the energy levels of yrast state is positively correlated with the square of the angular momentum. In this paper, the even-even nuclei, including 24Mg、28Si、46Ca、46Ti, and odd-mass nuclei, including 21Ne、43Sc, were calculated in the sd shell and pf shell model spaces in the presence of random interactions, which verifies the robustness of the non-collective rotational behavior in even-even nuclei with nonzero-spin ground state and odd-mass nuclei. Additionally, the linear correlation between the mathematical expectation of energy levels and the square of angular momentum is very good. When the minimum angular momentum level is higher than the maximum angular momentum level, the phenomenon of “reverse” non-collective rotation is also prevalent. Furthermore, we compare and discuss the influence of the ground states of even-even nuclei on the structure of yrast band, the results show that the even-even nuclei with nonzero-spin ground state will exhibit more randomness of the yrast band.
The non-collective rotational behavior of the yrast band is robustness for nuclei in the presence of random interactions, where the mathematical expectation of the energy levels of yrast state is positively correlated with the square of the angular momentum. In this paper, the even-even nuclei, including 24Mg、28Si、46Ca、46Ti, and odd-mass nuclei, including 21Ne、43Sc, were calculated in the sd shell and pf shell model spaces in the presence of random interactions, which verifies the robustness of the non-collective rotational behavior in even-even nuclei with nonzero-spin ground state and odd-mass nuclei. Additionally, the linear correlation between the mathematical expectation of energy levels and the square of angular momentum is very good. When the minimum angular momentum level is higher than the maximum angular momentum level, the phenomenon of “reverse” non-collective rotation is also prevalent. Furthermore, we compare and discuss the influence of the ground states of even-even nuclei on the structure of yrast band, the results show that the even-even nuclei with nonzero-spin ground state will exhibit more randomness of the yrast band.
2024, 41(1): 233-238.
doi: 10.11804/NuclPhysRev.41.2023CNPC34
Abstract:
Isospin symmetry breaking is essential to exploring atomic nuclear properties, offering vital insights that further our understanding of nuclear structure, reactions, and astrophysics. Mirror energy differences, a primary observational quantity in the study of isospin symmetry breaking, allow for a clear reflection of this phenomenon, which is significantly meaningful in comprehending the properties of nuclear forces. In light of the remarkable progress in supercomputing capabilities and quantum many-body techniques in atomic nuclei, ab initio calculations have achieved great success in nuclear systems. In this study, using the chiral effective field theory two-body and three-body forces, we employed the ab initio valence-space in-medium similarity renormalization group method to calculate the low-energy excited states of the mirror nuclei 25Si and 25Na. The nuclear forces adopted consider both charge symmetry breaking and charge independence breaking effects well, and the Coulomb force is also included in the quantum many-body Hamiltonian. The results show that the three-body forces are crucial in describing the excited states of nuclei. Based on the results of the excited states, we calculated the mirror energy differences and corresponding occupations of states in mirror nuclei. The results suggest that the larger mirror energy differences are primarily caused by occupying the weakly bound 1s1/2 orbit in proton-rich nuclei.
Isospin symmetry breaking is essential to exploring atomic nuclear properties, offering vital insights that further our understanding of nuclear structure, reactions, and astrophysics. Mirror energy differences, a primary observational quantity in the study of isospin symmetry breaking, allow for a clear reflection of this phenomenon, which is significantly meaningful in comprehending the properties of nuclear forces. In light of the remarkable progress in supercomputing capabilities and quantum many-body techniques in atomic nuclei, ab initio calculations have achieved great success in nuclear systems. In this study, using the chiral effective field theory two-body and three-body forces, we employed the ab initio valence-space in-medium similarity renormalization group method to calculate the low-energy excited states of the mirror nuclei 25Si and 25Na. The nuclear forces adopted consider both charge symmetry breaking and charge independence breaking effects well, and the Coulomb force is also included in the quantum many-body Hamiltonian. The results show that the three-body forces are crucial in describing the excited states of nuclei. Based on the results of the excited states, we calculated the mirror energy differences and corresponding occupations of states in mirror nuclei. The results suggest that the larger mirror energy differences are primarily caused by occupying the weakly bound 1s1/2 orbit in proton-rich nuclei.
2024, 41(1): 239-243.
doi: 10.11804/NuclPhysRev.41.2023CNPC53
Abstract:
High-spin states in 205Po have been investigated by using in-beam γ ray spectroscopy with the 196Pt(13C, 4n)205Po reaction at a beam energy of 72 MeV. The previously known level scheme has been extended, and 3 new decay sequence have been established by adding nineteen new γ rays. The yrast level structures in $^{203,\,205,\,207}{\rm{Po}}$ are compared with large-scale shell model calculations performed in a configuration space with the same proton and neutron orbits, which are 0h9/2, 1f5/2, 2p3/2, 2p1/2, 1g9/2. The calculated results are in reasonable agreement with experimental data.
High-spin states in 205Po have been investigated by using in-beam γ ray spectroscopy with the 196Pt(13C, 4n)205Po reaction at a beam energy of 72 MeV. The previously known level scheme has been extended, and 3 new decay sequence have been established by adding nineteen new γ rays. The yrast level structures in $^{203,\,205,\,207}{\rm{Po}}$ are compared with large-scale shell model calculations performed in a configuration space with the same proton and neutron orbits, which are 0h9/2, 1f5/2, 2p3/2, 2p1/2, 1g9/2. The calculated results are in reasonable agreement with experimental data.
2024, 41(1): 244-249.
doi: 10.11804/NuclPhysRev.41.2023CNPC12
Abstract:
High-spin level structure of 95Nb has been investigated using the multi-detector array of the conjoint gamma array in China via the 82Se(18O, p4n)95Nb. Based on γ-γ coincidence relationships, the level scheme of 95Nb has been modified and extended with 25 new γ rays and 15 new levels. The new level structure of 95Nb has been compared with the shell model calculations. It is suggested that the proton core excitation(f5/2→g9/2) across $Z = 38 $ sub-shell should be taken into account in order to adequately describe the high-spin level structure in 95Nb above spin of 39/2.
High-spin level structure of 95Nb has been investigated using the multi-detector array of the conjoint gamma array in China via the 82Se(18O, p4n)95Nb. Based on γ-γ coincidence relationships, the level scheme of 95Nb has been modified and extended with 25 new γ rays and 15 new levels. The new level structure of 95Nb has been compared with the shell model calculations. It is suggested that the proton core excitation(f5/2→g9/2) across $Z = 38 $ sub-shell should be taken into account in order to adequately describe the high-spin level structure in 95Nb above spin of 39/2.
2024, 41(1): 250-255.
doi: 10.11804/NuclPhysRev.41.2023CNPC10
Abstract:
High spin states of 94Nb have been studied with the 82Se(18O, p5n)94Nb fusion evaporation reaction at beam energy of 82 and 88 MeV. The experiment was performed at the HI-13 tandem accelerator of the China Institute of Atomic Energy. The previously reported level schemes of 94Nb have been extended and modified up to an excitation energy of 10.6 MeV and a spin and parity of 24(−) with 13 new γ-transitions. Based on DCO ratios and linear polarization measurements, spin-parity have been assiged up to the highest level observed. The level structures in 94Nb have been interpreted in terms of the shell model calculations performed in the configuration space π(1f5/2, 2p3/2, 2p1/2, 1g9/2 ) for the protons and ν(2p1/2, 1g9/2, 1g7/2, 2d5/2 ) for the neutrons, and the neutron proton excitation mechanism of 94Nb was discussed.
High spin states of 94Nb have been studied with the 82Se(18O, p5n)94Nb fusion evaporation reaction at beam energy of 82 and 88 MeV. The experiment was performed at the HI-13 tandem accelerator of the China Institute of Atomic Energy. The previously reported level schemes of 94Nb have been extended and modified up to an excitation energy of 10.6 MeV and a spin and parity of 24(−) with 13 new γ-transitions. Based on DCO ratios and linear polarization measurements, spin-parity have been assiged up to the highest level observed. The level structures in 94Nb have been interpreted in terms of the shell model calculations performed in the configuration space π(1f5/2, 2p3/2, 2p1/2, 1g9/2 ) for the protons and ν(2p1/2, 1g9/2, 1g7/2, 2d5/2 ) for the neutrons, and the neutron proton excitation mechanism of 94Nb was discussed.
2024, 41(1): 256-262.
doi: 10.11804/NuclPhysRev.41.2023CNPC27
Abstract:
Isomer with long lifetime and high excitation energy is of great significance in the fields of national strategic security and energy storage. Mastering the method of inducing isomer to decay is the key technology. However, this technology has got into trouble in recent years. For mastering the method of inducing isomer to decay, it is beneficial to start the research on the formation, excitation and de-excitation mechanism of isomer from the view of atomic nucleus structure. In this work, we used a white light neutron beam to bombard the Hf target in terms of experimental technology, and innovatively established a triple coincidence measurement system consisting of a barium fluoride detector array GTAF-Ⅱ for full energy measurement, a high-purity germanium detector for characteristic γ-ray measurement, and a white light neutron time-of-flight measurement. Through the analysis of experimental data, we found the sign of the 178Hf isomeric state exciting to the transition level and releasing rapidly.
Isomer with long lifetime and high excitation energy is of great significance in the fields of national strategic security and energy storage. Mastering the method of inducing isomer to decay is the key technology. However, this technology has got into trouble in recent years. For mastering the method of inducing isomer to decay, it is beneficial to start the research on the formation, excitation and de-excitation mechanism of isomer from the view of atomic nucleus structure. In this work, we used a white light neutron beam to bombard the Hf target in terms of experimental technology, and innovatively established a triple coincidence measurement system consisting of a barium fluoride detector array GTAF-Ⅱ for full energy measurement, a high-purity germanium detector for characteristic γ-ray measurement, and a white light neutron time-of-flight measurement. Through the analysis of experimental data, we found the sign of the 178Hf isomeric state exciting to the transition level and releasing rapidly.
2024, 41(1): 263-268.
doi: 10.11804/NuclPhysRev.41.2023CNPC62
Abstract:
The Atomic Mass Evaluation (AME) serves as a comprehensive source that collects and evaluates all experimental data related to atomic mass, including different techniques such as mass spectrometry, decay, and nuclear reactions. It is widely recognized as an authoritative and reliable repository of atomic masses in the world. In recent years, advancements in mass measurement technologies have significantly enhanced measurement precision, expanded the measurable range of nuclei, and unveiled new phenomena within exotic atomic nuclei. High-precision mass data provide indispensable references for fundamental nuclear physics research such as nuclear structure, nuclear reactions, and nuclear astrophysics. This article provides an overview of the latest Atomic Mass Evaluation, AME2020, and examines the accuracy of current major mass-measurements devices, and illustrates important experimental results. The release of AME2020 has profound practical implications for a wide range of scientific research and technological applications.
The Atomic Mass Evaluation (AME) serves as a comprehensive source that collects and evaluates all experimental data related to atomic mass, including different techniques such as mass spectrometry, decay, and nuclear reactions. It is widely recognized as an authoritative and reliable repository of atomic masses in the world. In recent years, advancements in mass measurement technologies have significantly enhanced measurement precision, expanded the measurable range of nuclei, and unveiled new phenomena within exotic atomic nuclei. High-precision mass data provide indispensable references for fundamental nuclear physics research such as nuclear structure, nuclear reactions, and nuclear astrophysics. This article provides an overview of the latest Atomic Mass Evaluation, AME2020, and examines the accuracy of current major mass-measurements devices, and illustrates important experimental results. The release of AME2020 has profound practical implications for a wide range of scientific research and technological applications.
2024, 41(1): 269-275.
doi: 10.11804/NuclPhysRev.41.2023CNPC20
Abstract:
Nuclear mass plays an important role in both nuclear physics and astrophysics. While the theoretical accuracy of masses has reached quite astonishing accuracy, their extrapolations have been conflicting, especially in neutron-rich regions. This paper reviews the main results of the extrapolations of nuclear mass models in recent years. By using a rigorous multi-objective optimization on mass models, we take the mass differences α decay energy and the Garvey-Kelson relations as multiple physical constraints to reduce the degree of overfitting phenomenon, resulting that the predictive power of models was improved in some degree. In addition, we use the improved mass data for the rapid neutron capture processes in nuclear astrophysics, further validating the reliability of the extrapolations.
Nuclear mass plays an important role in both nuclear physics and astrophysics. While the theoretical accuracy of masses has reached quite astonishing accuracy, their extrapolations have been conflicting, especially in neutron-rich regions. This paper reviews the main results of the extrapolations of nuclear mass models in recent years. By using a rigorous multi-objective optimization on mass models, we take the mass differences α decay energy and the Garvey-Kelson relations as multiple physical constraints to reduce the degree of overfitting phenomenon, resulting that the predictive power of models was improved in some degree. In addition, we use the improved mass data for the rapid neutron capture processes in nuclear astrophysics, further validating the reliability of the extrapolations.
2024, 41(1): 276-281.
doi: 10.11804/NuclPhysRev.41.2023CNPC23
Abstract:
The Lanzhou Heavy Ion Accelerator Cooling Storage Ring(HIRFL-CSR) is an ideal device for studying the decay of highly charged and short-lived isomers. In the lifetime measurement experiment of the short-lived highly charged ion $^{94m}{\rm{Ru}}^{44+}$, we directly observed the decay of $^{94}{\rm{Ru}}$ from 8+ isomer to the ground state, and identified 49 decay events in the observation time window of (20 μs, 180 μs). In order to identify more decay events, a new method based on amplitude of frequency spectrum was studied in this paper. Based on the simulation results, this new method can effectively identify decay events within (15 μs, 185 μs). By applying the new identification method to the experimental data processing, 54 decay events were identified within (15 μs, 185 μs). Based on these 54 decay events, the lifetime of $^{94m}{\rm{Ru}}^{44+}$ in the laboratory frame was calculated to be 194(121) μs. The new lifetime result is within the error range of the previous result 218(148) μs.
The Lanzhou Heavy Ion Accelerator Cooling Storage Ring(HIRFL-CSR) is an ideal device for studying the decay of highly charged and short-lived isomers. In the lifetime measurement experiment of the short-lived highly charged ion $^{94m}{\rm{Ru}}^{44+}$, we directly observed the decay of $^{94}{\rm{Ru}}$ from 8+ isomer to the ground state, and identified 49 decay events in the observation time window of (20 μs, 180 μs). In order to identify more decay events, a new method based on amplitude of frequency spectrum was studied in this paper. Based on the simulation results, this new method can effectively identify decay events within (15 μs, 185 μs). By applying the new identification method to the experimental data processing, 54 decay events were identified within (15 μs, 185 μs). Based on these 54 decay events, the lifetime of $^{94m}{\rm{Ru}}^{44+}$ in the laboratory frame was calculated to be 194(121) μs. The new lifetime result is within the error range of the previous result 218(148) μs.
2024, 41(1): 282-287.
doi: 10.11804/NuclPhysRev.41.2023CNPC05
Abstract:
In this work, the Gamow-like model for calculating the one-proton radioactivity half-life is improved by introducing the deformation of the nucleus. The calculations show that the deformed Gamow-like model can reproduce the experimental data better than the Gamow-like model. In addition, the reliability of the deformed Gamow-like model is confirmed by studying the linear relationship between the logarithmic form of the experimental half-life and the logarithmic form of the theoretical penetration probability. As an application, the one-proton radioactivity half-life of the deformed nucleus is predicted using the deformed Gamow-like model, and the predictions are able to comply well with the Geiger-Nuttall law. Finally, by studying the relationship between the orbital angular momentum and the calculated half-life, the reference values of the orbital angular momentum of 109I and 131Eu are given to obtain a more accurate theoretical half-life for one-proton radioactivity.
In this work, the Gamow-like model for calculating the one-proton radioactivity half-life is improved by introducing the deformation of the nucleus. The calculations show that the deformed Gamow-like model can reproduce the experimental data better than the Gamow-like model. In addition, the reliability of the deformed Gamow-like model is confirmed by studying the linear relationship between the logarithmic form of the experimental half-life and the logarithmic form of the theoretical penetration probability. As an application, the one-proton radioactivity half-life of the deformed nucleus is predicted using the deformed Gamow-like model, and the predictions are able to comply well with the Geiger-Nuttall law. Finally, by studying the relationship between the orbital angular momentum and the calculated half-life, the reference values of the orbital angular momentum of 109I and 131Eu are given to obtain a more accurate theoretical half-life for one-proton radioactivity.
2024, 41(1): 288-291.
doi: 10.11804/NuclPhysRev.41.2023CNPC49
Abstract:
Understanding deeply the properties of the ground and excited states of 7Li and 7Be is important for explaining the creation and related reactions of Li and Be isotopes in the primordial universe. Most of the cluster model calculations of 7Li or 7Be consider only the $\alpha+{\mathrm{t}} $ or α+3He two-body cluster structure. The present work conducted theoretical research employing a four-body microscopic cluster model. The results show that, by considering the three- and four-body cluster structures, the calculated wave functions of ground and excited states are effectively modified. The obtained observables such as energy spectra and nuclear radii reproduce better the experimental data, compared to that in the two-body calculation.
Understanding deeply the properties of the ground and excited states of 7Li and 7Be is important for explaining the creation and related reactions of Li and Be isotopes in the primordial universe. Most of the cluster model calculations of 7Li or 7Be consider only the $\alpha+{\mathrm{t}} $ or α+3He two-body cluster structure. The present work conducted theoretical research employing a four-body microscopic cluster model. The results show that, by considering the three- and four-body cluster structures, the calculated wave functions of ground and excited states are effectively modified. The obtained observables such as energy spectra and nuclear radii reproduce better the experimental data, compared to that in the two-body calculation.
2024, 41(1): 292-298.
doi: 10.11804/NuclPhysRev.41.2023CNPC35
Abstract:
Recently, an inelastic scattering experiment of 16O+12C was performed at the Beijing Tandem Accelerator Nuclear Physics National of China Institute of Atomic Energy. New evidence for the existence of Bose-Einstein condensation state of 16O has been obtained. Employing a series of double-sided-silicon-strip-based telescopes, this experiment achieved accurate particle identification and coincidence measurement of 4-α in the decay of 16O for the first time. Based on this, high-resolution reaction Q-value spectra was obtained and clear 4-α resonance states were reconstructed. In the vicinity of the 4-α separation threshold, 4 highly significant (3 of them above 5σ) resonance states were observed, which decay to the characteristic pattern of 12C(Hoyle state)+α, consistent with the predicted Hoyle-BEC structure and its rotating band features. The observation results will promote further theoretical research, and more measurements are needed for these resonance states in experiments.
Recently, an inelastic scattering experiment of 16O+12C was performed at the Beijing Tandem Accelerator Nuclear Physics National of China Institute of Atomic Energy. New evidence for the existence of Bose-Einstein condensation state of 16O has been obtained. Employing a series of double-sided-silicon-strip-based telescopes, this experiment achieved accurate particle identification and coincidence measurement of 4-α in the decay of 16O for the first time. Based on this, high-resolution reaction Q-value spectra was obtained and clear 4-α resonance states were reconstructed. In the vicinity of the 4-α separation threshold, 4 highly significant (3 of them above 5σ) resonance states were observed, which decay to the characteristic pattern of 12C(Hoyle state)+α, consistent with the predicted Hoyle-BEC structure and its rotating band features. The observation results will promote further theoretical research, and more measurements are needed for these resonance states in experiments.
2024, 41(1): 299-307.
doi: 10.11804/NuclPhysRev.41.2023CNPC07
Abstract:
Relativistic Brueckner-Hartree-Fock(RBHF) theory is one of the most important ab initio methods in the relativistic framework, where the saturation properties of nuclear matter could be described satisfactorily with only considering two-body forces. By achieving the self-consistent solution of the RBHF equations for nuclear matter in the full Dirac space, the scalar and vector components of the single-particle potential have been determined uniquely, the uncertainties caused by the neglect of negative-energy states(NESs) have been avoided, and the long-standing problem over 40 years of not being able to uniquely determine the single-particle potential has been solved. The history of the RBHF theory is briefly reviewed, and the necessity of considering NESs is illustrated. The latest results of nuclear matter and neutron star matter by the RBHF theory in the full Dirac space are discussed, including the effective mass, the binding energy per particle of pure neutron matter, the pressure of symmetric nuclear matter and pure neutron matter, the particle fractions as well as the equation of state for neutron star matter, and the mass-radius relation as well as the tidal deformability of a neutron star. Possible applications of the RBHF theory in the full Dirac space are also discussed, including the calibration of the parameters in density functional theory, the microscopic description of nucleon-nucleus elastic scattering, and the research on the hadron-quark transition inside neutron stars.
Relativistic Brueckner-Hartree-Fock(RBHF) theory is one of the most important ab initio methods in the relativistic framework, where the saturation properties of nuclear matter could be described satisfactorily with only considering two-body forces. By achieving the self-consistent solution of the RBHF equations for nuclear matter in the full Dirac space, the scalar and vector components of the single-particle potential have been determined uniquely, the uncertainties caused by the neglect of negative-energy states(NESs) have been avoided, and the long-standing problem over 40 years of not being able to uniquely determine the single-particle potential has been solved. The history of the RBHF theory is briefly reviewed, and the necessity of considering NESs is illustrated. The latest results of nuclear matter and neutron star matter by the RBHF theory in the full Dirac space are discussed, including the effective mass, the binding energy per particle of pure neutron matter, the pressure of symmetric nuclear matter and pure neutron matter, the particle fractions as well as the equation of state for neutron star matter, and the mass-radius relation as well as the tidal deformability of a neutron star. Possible applications of the RBHF theory in the full Dirac space are also discussed, including the calibration of the parameters in density functional theory, the microscopic description of nucleon-nucleus elastic scattering, and the research on the hadron-quark transition inside neutron stars.
2024, 41(1): 308-317.
doi: 10.11804/NuclPhysRev.41.2023CNPC36
Abstract:
The equation of state of dense matter in neutron stars holds significant research significance in nuclear astrophysics, astrophysics, and dense QCD phase structure. It plays a decisive role in the structure, formation, and evolution of these stars. The direct detection of gravitational waves by LIGO has ushered in a golden age of neutron star research. This article presents our research progress on neutron star strangeness phase transitions, hyperon puzzle, and the evolution of temperature and frequency. We combine nuclear physics and astronomy to analyze these phenomena and also discuss ways of distinguishing different types of neutron stars based on current multi-messenger observations and model calculations of microscopic parameters in the equation of state.
The equation of state of dense matter in neutron stars holds significant research significance in nuclear astrophysics, astrophysics, and dense QCD phase structure. It plays a decisive role in the structure, formation, and evolution of these stars. The direct detection of gravitational waves by LIGO has ushered in a golden age of neutron star research. This article presents our research progress on neutron star strangeness phase transitions, hyperon puzzle, and the evolution of temperature and frequency. We combine nuclear physics and astronomy to analyze these phenomena and also discuss ways of distinguishing different types of neutron stars based on current multi-messenger observations and model calculations of microscopic parameters in the equation of state.
2024, 41(1): 318-324.
doi: 10.11804/NuclPhysRev.41.2023CNPC21
Abstract:
The cores of massive neutron stars can reach densities 5~10 times that of nuclear saturation density, where hadron deconfinement phase transition is highly plausible. In this work, we investigate the structural properties of the hadron-quark mixed phases and their impact on the characteristics of neutron stars. Furthermore, we delve into the possibility of the existence of a pure quark phase core within neutron stars. We investigate the properties of the hadron-quarkpastaphases and their influences on the equation of state (EOS) for neutron stars. In this work, we extend the energy minimization (EM) method to describe the hadron-quarkpastaphase, where the surface and Coulomb contributions are included in the minimization procedure. By allowing different electron densities in the hadronic and quark matter phases, the total electron chemical potential with the electric potential remains constant, and local β equilibrium is achieved inside the Wigner-Seitz cell. We employ the relativistic mean-field model to describe the hadronic matter, while the quark matter is described by the MIT bag model with vector interactions. It is found that the vector interactions among quarks can significantly stiffen the EOS at high densities and help enhance the maximum mass of neutron stars. Other parameters like the bag constant can also affect the deconfinement phase transition in neutron stars. Our results show that hadron-quarkpastaphases may appear in the core of massive neutron stars that can be compatible with current observational constraints.
The cores of massive neutron stars can reach densities 5~10 times that of nuclear saturation density, where hadron deconfinement phase transition is highly plausible. In this work, we investigate the structural properties of the hadron-quark mixed phases and their impact on the characteristics of neutron stars. Furthermore, we delve into the possibility of the existence of a pure quark phase core within neutron stars. We investigate the properties of the hadron-quarkpastaphases and their influences on the equation of state (EOS) for neutron stars. In this work, we extend the energy minimization (EM) method to describe the hadron-quarkpastaphase, where the surface and Coulomb contributions are included in the minimization procedure. By allowing different electron densities in the hadronic and quark matter phases, the total electron chemical potential with the electric potential remains constant, and local β equilibrium is achieved inside the Wigner-Seitz cell. We employ the relativistic mean-field model to describe the hadronic matter, while the quark matter is described by the MIT bag model with vector interactions. It is found that the vector interactions among quarks can significantly stiffen the EOS at high densities and help enhance the maximum mass of neutron stars. Other parameters like the bag constant can also affect the deconfinement phase transition in neutron stars. Our results show that hadron-quarkpastaphases may appear in the core of massive neutron stars that can be compatible with current observational constraints.
2024, 41(1): 325-330.
doi: 10.11804/NuclPhysRev.41.2023CNPC09
Abstract:
Research performed during the past decade revealed an important role of symmetry energy in the equation of state of quark matter. By introducing an isospin-dependent term into the quark mass scaling, the stability window of quark matter was studied in the equivparticle model. The results show that a sufficiently strong isospin dependence $ C_I $ can significantly widen the absolute stable region of strange quark matter, yielding results that simultaneously satisfy the constraints of the astrophysical observations of PSR J1614-2230 with (1.928 ± 0.017) $ {{M}}_\odot $ and tidal deformability $ 70 \leqslant \varLambda_{1.4} \leqslant 580 $ measured in the event GW170817. Contrary to the case of strange quark matter, the stable region of u-d quark matter narrows with isospin dependence $ C_I $, leading to inconsistency with astrophysical observations. Finally, we found that the symmetry energy of strange quark matter is much larger than that of u-d quark matter, and one-gluon exchange interaction between quarks causes the symmetry energy of strange quark matter to become softer.
Research performed during the past decade revealed an important role of symmetry energy in the equation of state of quark matter. By introducing an isospin-dependent term into the quark mass scaling, the stability window of quark matter was studied in the equivparticle model. The results show that a sufficiently strong isospin dependence $ C_I $ can significantly widen the absolute stable region of strange quark matter, yielding results that simultaneously satisfy the constraints of the astrophysical observations of PSR J1614-2230 with (1.928 ± 0.017) $ {{M}}_\odot $ and tidal deformability $ 70 \leqslant \varLambda_{1.4} \leqslant 580 $ measured in the event GW170817. Contrary to the case of strange quark matter, the stable region of u-d quark matter narrows with isospin dependence $ C_I $, leading to inconsistency with astrophysical observations. Finally, we found that the symmetry energy of strange quark matter is much larger than that of u-d quark matter, and one-gluon exchange interaction between quarks causes the symmetry energy of strange quark matter to become softer.
2024, 41(1): 331-339.
doi: 10.11804/NuclPhysRev.41.2023CNPC60
Abstract:
Dark matter admixed neutron stars are neutron stars that contain dark matter in their composition. In this paper, we mainly study the universal relation between the properties of Dark matter admixed neutron stars. The results show that similar to the results of normal neutron stars, there is also a universal relation between the relevant properties of dark matter admixed neutron stars. The change of the particles mass and the mass ratio of dark matter will cause the observed distinguishable effect between Dark matter admixed neutron stars and normal neutron stars. There exists exponential form of universal relations between the tidal deformability Λ, dimensionless gravitational binding energy Eg/M and the dimensionless moment of inertia I/M3.
Dark matter admixed neutron stars are neutron stars that contain dark matter in their composition. In this paper, we mainly study the universal relation between the properties of Dark matter admixed neutron stars. The results show that similar to the results of normal neutron stars, there is also a universal relation between the relevant properties of dark matter admixed neutron stars. The change of the particles mass and the mass ratio of dark matter will cause the observed distinguishable effect between Dark matter admixed neutron stars and normal neutron stars. There exists exponential form of universal relations between the tidal deformability Λ, dimensionless gravitational binding energy Eg/M and the dimensionless moment of inertia I/M3.
2024, 41(1): 340-345.
doi: 10.11804/NuclPhysRev.41.2023CNPC75
Abstract:
In thermonuclear reactions of nuclear astrophysical interest, some can produce short-lived products that emit positrons. These positrons will annihilate with electrons in the target and then produce a pair of 511 keV γ-rays, which can be used to determine the reaction yield and calculate the cross-section as well as the astrophysical S-factor. Recently, an in situ measurement method for positron annihilation on experimental terminals has been proposed. This method takes advantage of the characteristic opposite direction of the 511 keV γ-ray pairs and uses the opposite units in the detection array for spatial coincidence measurements to suppress background. In this study, we investigated this method using the newly developed large modular BGO detector array LAMBDA-II. The results show that the detection efficiency of LAMBDA-II for in situ β+ decay of reaction products is (7.6±0.2)%, which is in good agreement with the value given by Monte Carlo simulations. The yield of the 14N(p, γ)15O 259 keV resonance determined by in situ measurement agrees well with that derived from prompt γ-ray measurement, verifying the reliability of this method and providing a solid foundation for its further application in nuclear astrophysics research.
In thermonuclear reactions of nuclear astrophysical interest, some can produce short-lived products that emit positrons. These positrons will annihilate with electrons in the target and then produce a pair of 511 keV γ-rays, which can be used to determine the reaction yield and calculate the cross-section as well as the astrophysical S-factor. Recently, an in situ measurement method for positron annihilation on experimental terminals has been proposed. This method takes advantage of the characteristic opposite direction of the 511 keV γ-ray pairs and uses the opposite units in the detection array for spatial coincidence measurements to suppress background. In this study, we investigated this method using the newly developed large modular BGO detector array LAMBDA-II. The results show that the detection efficiency of LAMBDA-II for in situ β+ decay of reaction products is (7.6±0.2)%, which is in good agreement with the value given by Monte Carlo simulations. The yield of the 14N(p, γ)15O 259 keV resonance determined by in situ measurement agrees well with that derived from prompt γ-ray measurement, verifying the reliability of this method and providing a solid foundation for its further application in nuclear astrophysics research.
2024, 41(1): 346-351.
doi: 10.11804/NuclPhysRev.41.2023CNPC30
Abstract:
The feasibility of producing superheavy nuclei in proton evaporation channels was systematically studied within the dinuclear system (DNS) model. Due to the $Z = 114$ proton-shell, one can synthesize Fl isotopes in proton evaporation channels. We only considered the case of evaporating one proton first and then n neutrons in this work, other cases were ignored due to the small cross-section. The production cross sections of unknown isotopes 290, 291Fl in 38S+255Es reaction are the highest compared with 50Ti+243Np and 54Cr+239Pa reactions, and the maximum cross sections are 1.1 and 15.1 pb, respectively. 42S+254Es is a promising candidate to approach the island of stability as the radioactive beam facilities are upgraded in the future, and the production cross sections of 291−294Fl in that reaction are estimated to be 3.2, 6.0, 4.0, and 0.1 pb, respectively.
The feasibility of producing superheavy nuclei in proton evaporation channels was systematically studied within the dinuclear system (DNS) model. Due to the $Z = 114$ proton-shell, one can synthesize Fl isotopes in proton evaporation channels. We only considered the case of evaporating one proton first and then n neutrons in this work, other cases were ignored due to the small cross-section. The production cross sections of unknown isotopes 290, 291Fl in 38S+255Es reaction are the highest compared with 50Ti+243Np and 54Cr+239Pa reactions, and the maximum cross sections are 1.1 and 15.1 pb, respectively. 42S+254Es is a promising candidate to approach the island of stability as the radioactive beam facilities are upgraded in the future, and the production cross sections of 291−294Fl in that reaction are estimated to be 3.2, 6.0, 4.0, and 0.1 pb, respectively.
2024, 41(1): 352-359.
doi: 10.11804/NuclPhysRev.41.2023CNPC37
Abstract:
The nuclear reaction at energies near the Coulomb barrier is an effective way to study the interaction between nuclear structure and dynamics. As more exotic weakly bound nuclei become accessible at new accelerator facilities, it is becoming critically important to understand the influence of weak binding energy on reaction dynamics, including on fusion. At present, a large number of experiments have shown that the complete fusion cross section between stable weakly bound nuclei such as 6, 7Li, 9Be and heavy mass target nuclei is suppressed about 30% lower than the fusion cross section calculated by existing theoretical models and the fusion cross-section derived from tightly bound nuclear systems. In order to investigate the breakup effect of weakly bound nuclei on the suppression of the complete fusion cross section, studying the breakup reaction and mechanism of weakly bound nuclei has become concerned. Currently, research groups both domestically and internationally have conducted studies on the breakup reactions of weakly bound nuclei by coincidence measurement. It is concluded that the suppression of the above-barrier complete fusion cross section of the weakly bound nuclei is mainly caused by the prompt breakup of the projectile-like nuclei formed through the transfer of the weakly bound nuclei, and the relative contributions of different breakup channels to the suppression of the complete fusion were obtained. Our research group has also conducted experiments on the breakup mechanism of 6, 7Li+209Bi based on a large solid-angle coverage array. The beam energies were set at 30, 40, and 47 MeV. We successfully identified the components of prompt breakup and resonant breakup for the α+α, α+t, α+d, and α+p breakup channels. For the first time in the 6Li+209Bi experimental data, the α+t break-up channel was observed, further refining the understanding of the break-up reaction mechanism for 6, 7Li+209Bi.
The nuclear reaction at energies near the Coulomb barrier is an effective way to study the interaction between nuclear structure and dynamics. As more exotic weakly bound nuclei become accessible at new accelerator facilities, it is becoming critically important to understand the influence of weak binding energy on reaction dynamics, including on fusion. At present, a large number of experiments have shown that the complete fusion cross section between stable weakly bound nuclei such as 6, 7Li, 9Be and heavy mass target nuclei is suppressed about 30% lower than the fusion cross section calculated by existing theoretical models and the fusion cross-section derived from tightly bound nuclear systems. In order to investigate the breakup effect of weakly bound nuclei on the suppression of the complete fusion cross section, studying the breakup reaction and mechanism of weakly bound nuclei has become concerned. Currently, research groups both domestically and internationally have conducted studies on the breakup reactions of weakly bound nuclei by coincidence measurement. It is concluded that the suppression of the above-barrier complete fusion cross section of the weakly bound nuclei is mainly caused by the prompt breakup of the projectile-like nuclei formed through the transfer of the weakly bound nuclei, and the relative contributions of different breakup channels to the suppression of the complete fusion were obtained. Our research group has also conducted experiments on the breakup mechanism of 6, 7Li+209Bi based on a large solid-angle coverage array. The beam energies were set at 30, 40, and 47 MeV. We successfully identified the components of prompt breakup and resonant breakup for the α+α, α+t, α+d, and α+p breakup channels. For the first time in the 6Li+209Bi experimental data, the α+t break-up channel was observed, further refining the understanding of the break-up reaction mechanism for 6, 7Li+209Bi.
2024, 41(1): 360-365.
doi: 10.11804/NuclPhysRev.41.2023CNPC57
Abstract:
Trajectory corrections to the eikonal approximation for the distortions of the projectile trajectory caused by Coulomb potential only, Coulomb+real part of the optical model potential (OMP), and Coulomb+both real and imaginary parts of the OMP, are studied. The necessity of including the imaginary parts of the OMPs in such corrections is demonstrated with the calculations of the elastic scattering angular distributions of 16O on12C, 63Cu and 208Pb targets at incident energies from 12.5 to 50 MeV/u. Complex trajectory correction is found to be especially important for light and intermediate-mass targets. Root mean square (rms) radii of light-heavy nuclei 6−9, 11Li, 9−12Be, 10−15B, 11, 12, 14−18C, 14, 16−19N, and 15, 17, 19−21O, were obtained from reanalysis of the total reaction cross sections of these nuclei on a natCu target at 25~65 MeV/u incident energies with the complex trajectory corrections. The overall deviation, between the rms radii obtained by Liatard et al. using Glauber model to analyze this data and the rms radii obtained by Ozawa et al. using Glauber model to analyze the high-energy total interaction cross section data with incident energies of about 650~1 020 MeV/u, is 7.7%. The corresponding deviation of the analysis results in this work is 1.9%.
Trajectory corrections to the eikonal approximation for the distortions of the projectile trajectory caused by Coulomb potential only, Coulomb+real part of the optical model potential (OMP), and Coulomb+both real and imaginary parts of the OMP, are studied. The necessity of including the imaginary parts of the OMPs in such corrections is demonstrated with the calculations of the elastic scattering angular distributions of 16O on12C, 63Cu and 208Pb targets at incident energies from 12.5 to 50 MeV/u. Complex trajectory correction is found to be especially important for light and intermediate-mass targets. Root mean square (rms) radii of light-heavy nuclei 6−9, 11Li, 9−12Be, 10−15B, 11, 12, 14−18C, 14, 16−19N, and 15, 17, 19−21O, were obtained from reanalysis of the total reaction cross sections of these nuclei on a natCu target at 25~65 MeV/u incident energies with the complex trajectory corrections. The overall deviation, between the rms radii obtained by Liatard et al. using Glauber model to analyze this data and the rms radii obtained by Ozawa et al. using Glauber model to analyze the high-energy total interaction cross section data with incident energies of about 650~1 020 MeV/u, is 7.7%. The corresponding deviation of the analysis results in this work is 1.9%.
2024, 41(1): 366-370.
doi: 10.11804/NuclPhysRev.41.2023CNPC32
Abstract:
The neutron capture cross sections of unstable nuclei are important to the study of the stellar nucleosynthesis and the neutron densities in massive stars. Due to the difficulties of the target fabrication, it is very hard to measure the neutron capture cross section of unstable nuclei directly. Therefore, the surrogate ratio method had been employed in (n, γ) determination and proved valid previously. In this work, the difference of the spin-parity distribution in compound nuclei that formed by surrogate reaction or neutron capture was discussed in (n, γ) determination with surrogate ratio method. The γ-decay probabilities ratio of 92Zr* and 94Zr* were calculated in various spin-parities, and the calculation showed the ratio is insensitive to their spin-parity distribution in high incident neutron energies. The measured γ-decay probabilities ratios of 92Zr* and 94Zr* were compared to the theoretical calculations, it imply that the spin-parity distributions of compound nuclei formed by (18O, 16O) reactions are similar to the one formed by neutron captures, and the validity of the surrogate ratio method was further proved in this work.
The neutron capture cross sections of unstable nuclei are important to the study of the stellar nucleosynthesis and the neutron densities in massive stars. Due to the difficulties of the target fabrication, it is very hard to measure the neutron capture cross section of unstable nuclei directly. Therefore, the surrogate ratio method had been employed in (n, γ) determination and proved valid previously. In this work, the difference of the spin-parity distribution in compound nuclei that formed by surrogate reaction or neutron capture was discussed in (n, γ) determination with surrogate ratio method. The γ-decay probabilities ratio of 92Zr* and 94Zr* were calculated in various spin-parities, and the calculation showed the ratio is insensitive to their spin-parity distribution in high incident neutron energies. The measured γ-decay probabilities ratios of 92Zr* and 94Zr* were compared to the theoretical calculations, it imply that the spin-parity distributions of compound nuclei formed by (18O, 16O) reactions are similar to the one formed by neutron captures, and the validity of the surrogate ratio method was further proved in this work.
2024, 41(1): 371-378.
doi: 10.11804/NuclPhysRev.41.2023CNPC31
Abstract:
The angle-differential cross sections of neutron-induced d production from carbon were measured at 12 neutron energies at Back-n white neutron source of China Spallation Neutron Source (CSNS). By employing the $ {\varDelta}E-E $ telescopes of the Light-charged Particle Detector Array (LPDA) system from $ 24.5^{\circ} $ to $ 155.5^{\circ} $ in the laboratory system, the angle-differential cross sections of the $^{12}{\rm C}({\rm{n}},{\rm{d}})x$ reactions were measured. The experimental results are in good agreement with the previous ones. The present work can provide a reference to the data library considering the lack of experimental data.
The angle-differential cross sections of neutron-induced d production from carbon were measured at 12 neutron energies at Back-n white neutron source of China Spallation Neutron Source (CSNS). By employing the $ {\varDelta}E-E $ telescopes of the Light-charged Particle Detector Array (LPDA) system from $ 24.5^{\circ} $ to $ 155.5^{\circ} $ in the laboratory system, the angle-differential cross sections of the $^{12}{\rm C}({\rm{n}},{\rm{d}})x$ reactions were measured. The experimental results are in good agreement with the previous ones. The present work can provide a reference to the data library considering the lack of experimental data.
2024, 41(1): 379-384.
doi: 10.11804/NuclPhysRev.41.2023CNPC51
Abstract:
Artificial Neural Network (ANN) has become a powerful tool in the field of scientific research with its powerful information encapsulation ability and convenient variational optimization method. In particular, there have been many recent advances in computational physics to solve variational problems. Deep Neural Network (DNN) is used to represent the wave function to solve quantum many-body problems using variational optimization. In this work we used a new Physics-Informed Neural Network (PINN) to represent the Cumulative Distribution Function (CDF) of some classical problems in quantum mechanics and to obtain their ground state wave function and ground state energy through the CDF. By benchmarking against the exact solution, the error of the results can be controlled at a very low level. This new network architecture and optimization method can provide a new choice for solving quantum many-body problems.
Artificial Neural Network (ANN) has become a powerful tool in the field of scientific research with its powerful information encapsulation ability and convenient variational optimization method. In particular, there have been many recent advances in computational physics to solve variational problems. Deep Neural Network (DNN) is used to represent the wave function to solve quantum many-body problems using variational optimization. In this work we used a new Physics-Informed Neural Network (PINN) to represent the Cumulative Distribution Function (CDF) of some classical problems in quantum mechanics and to obtain their ground state wave function and ground state energy through the CDF. By benchmarking against the exact solution, the error of the results can be controlled at a very low level. This new network architecture and optimization method can provide a new choice for solving quantum many-body problems.
2024, 41(1): 385-395.
doi: 10.11804/NuclPhysRev.41.2023CNPC13
Abstract:
The neural network model is used to learn and simulate the ground state spin distribution of the nucleus under stochastic two-system ensemble (TBRE), and the input characteristics of the learned model are analyzed. This is a typical application of classification using neural network models in nuclear physics. We show that it is still difficult to accurately each the sample within random interaction ensemble using the single hidden layer neural network model in this paper. However, the NN model describes the statistical properties of the ground state spins reasonably well, probably because the NN model learned the empirical law of the ground state spin distribution in TBRE.
The neural network model is used to learn and simulate the ground state spin distribution of the nucleus under stochastic two-system ensemble (TBRE), and the input characteristics of the learned model are analyzed. This is a typical application of classification using neural network models in nuclear physics. We show that it is still difficult to accurately each the sample within random interaction ensemble using the single hidden layer neural network model in this paper. However, the NN model describes the statistical properties of the ground state spins reasonably well, probably because the NN model learned the empirical law of the ground state spin distribution in TBRE.
2024, 41(1): 396-401.
doi: 10.11804/NuclPhysRev.41.2023CNPC85
Abstract:
Nuclear data is the basis for nuclear physics fundamental research, nuclear engineering, and applications in nuclear technology. Neutron-induced nuclear fission reaction cross-sections are a primary component of nuclear data, with significant applications in advanced nuclear energy system development and nuclear astrophysics research. This work, based on Bayesian theory, employs a feedforward neural network with four hidden layers. The Markov Chain Monte Carlo (MCMC) simulation method and Kullback–Leibler divergence (KL) are utilized. A Bayesian neural network computational model is established for neutron-induced fission reaction cross-section data of 238U, 232Th, and 239Pu, with incident energy and fission cross-section as input and output parameters, respectively. Experimental data and evaluation data of fission cross-sections for 238U and 232Th in the neutron energy range of 1~200 MeV and for 239Pu in the range of 1~100 MeV are selected for model training. The MCMC method is employed to construct a Markov chain to approximate the target distribution, and the KL divergence constraint method is combined to optimize the loss function. The research results indicate that the Bayesian neural network prediction model can effectively reproduce experimental data from literature, demonstrating strong predictive capabilities. This provides a reference for addressing the significant discrepancies in experimental data for 238U and 232Th with incident neutron energies greater than 200 MeV and for 239Pu with energies greater than 100 MeV, as well as for nuclear data evaluation.
Nuclear data is the basis for nuclear physics fundamental research, nuclear engineering, and applications in nuclear technology. Neutron-induced nuclear fission reaction cross-sections are a primary component of nuclear data, with significant applications in advanced nuclear energy system development and nuclear astrophysics research. This work, based on Bayesian theory, employs a feedforward neural network with four hidden layers. The Markov Chain Monte Carlo (MCMC) simulation method and Kullback–Leibler divergence (KL) are utilized. A Bayesian neural network computational model is established for neutron-induced fission reaction cross-section data of 238U, 232Th, and 239Pu, with incident energy and fission cross-section as input and output parameters, respectively. Experimental data and evaluation data of fission cross-sections for 238U and 232Th in the neutron energy range of 1~200 MeV and for 239Pu in the range of 1~100 MeV are selected for model training. The MCMC method is employed to construct a Markov chain to approximate the target distribution, and the KL divergence constraint method is combined to optimize the loss function. The research results indicate that the Bayesian neural network prediction model can effectively reproduce experimental data from literature, demonstrating strong predictive capabilities. This provides a reference for addressing the significant discrepancies in experimental data for 238U and 232Th with incident neutron energies greater than 200 MeV and for 239Pu with energies greater than 100 MeV, as well as for nuclear data evaluation.
2024, 41(1): 402-408.
doi: 10.11804/NuclPhysRev.41.2023CNPC64
Abstract:
The structure of neutron-rich nuclei in the neutron drip line region is one of the frontiers of the Radioactive Ion Beam physics. By directly detecting the neutrons emitted during their decay, the multi-neutron correlations of the nucleus can be extracted, which also provides critical information for the study of the properties of neutron-rich nuclear matter. In order to meet the requirements of conducting multi-neutron detection experiments, we developed a machine-learning-based multi-neutron recognition algorithm. We constructed a deep neural network to determine the number of incident neutrons event by event, and to further select the real neutron signals. The results of this work indicate that the detection efficiency of the machine learning algorithm is ~15%, whereas that of the traditional algorithm is ~1%. The machine learning algorithm can significantly improve four-neutron detection efficiency by more than 10 times, and is expected to be applied to multi-neutron detection experiments.
The structure of neutron-rich nuclei in the neutron drip line region is one of the frontiers of the Radioactive Ion Beam physics. By directly detecting the neutrons emitted during their decay, the multi-neutron correlations of the nucleus can be extracted, which also provides critical information for the study of the properties of neutron-rich nuclear matter. In order to meet the requirements of conducting multi-neutron detection experiments, we developed a machine-learning-based multi-neutron recognition algorithm. We constructed a deep neural network to determine the number of incident neutrons event by event, and to further select the real neutron signals. The results of this work indicate that the detection efficiency of the machine learning algorithm is ~15%, whereas that of the traditional algorithm is ~1%. The machine learning algorithm can significantly improve four-neutron detection efficiency by more than 10 times, and is expected to be applied to multi-neutron detection experiments.
2024, 41(1): 409-417.
doi: 10.11804/NuclPhysRev.41.2023CNPC22
Abstract:
The space charge effect is the core problem of high intensity proton accelerator, especially at injection and initial acceleration stages. Using the phase space painting with optimized process, will effectively reduce the influence of space charge effect on injection and acceleration efficiency, and emittance increase. Transverse phase space painting methods can be divided into correlated painting and anti-correlated painting. In this paper, firstly, the transverse phase space paintings for the high intensity proton synchrotron are discussed in detail, including different painting methods and different implementation methods. Secondly, based on the injection system of the China Spallation Neutron Source (CSNS), the beam injection process and anti-correlated painting design scheme are studied in detail. The reasons for the reduction of the actual vertical painting range and the influence of edge focusing effects of the bump magnets on the painting and beam dynamics are deeply explored. In addition, the method to perform the correlated painting based on the mechanical structure of the anti-correlated painting scheme and its key role in realizing the CSNS design goal are briefly introduced. Finally, according to the requirement of switching between different painting methods online in future accelerators, a new injection scheme that can realize correlated and anti-correlated painting simultaneously has been proposed. The new painting injection scheme has been demonstrated, simulated and optimized in detail.
The space charge effect is the core problem of high intensity proton accelerator, especially at injection and initial acceleration stages. Using the phase space painting with optimized process, will effectively reduce the influence of space charge effect on injection and acceleration efficiency, and emittance increase. Transverse phase space painting methods can be divided into correlated painting and anti-correlated painting. In this paper, firstly, the transverse phase space paintings for the high intensity proton synchrotron are discussed in detail, including different painting methods and different implementation methods. Secondly, based on the injection system of the China Spallation Neutron Source (CSNS), the beam injection process and anti-correlated painting design scheme are studied in detail. The reasons for the reduction of the actual vertical painting range and the influence of edge focusing effects of the bump magnets on the painting and beam dynamics are deeply explored. In addition, the method to perform the correlated painting based on the mechanical structure of the anti-correlated painting scheme and its key role in realizing the CSNS design goal are briefly introduced. Finally, according to the requirement of switching between different painting methods online in future accelerators, a new injection scheme that can realize correlated and anti-correlated painting simultaneously has been proposed. The new painting injection scheme has been demonstrated, simulated and optimized in detail.
2024, 41(1): 433-438.
doi: 10.11804/NuclPhysRev.41.2023CNPC42
Abstract:
Shanghai Laser Electron Gamma Source (SLEGS) is a quasi-monoenergetic, and energy-tunable MeV gamma-rays source generated by the inverse Laser Compton Scattering (LCS) of lasers and electrons. SLEGS is the only LCS gamma source in the world with a continuously variable collision angular range. The gamma activation analysis is one of the effective methods to study the properties of materials. This paper introduces the gamma activation platform of SLEGS, including the online activation experiment, the low background offline measurement, and the energy and efficiency calibration for the high purity germanium (HPGe) detector. The counting rate of the shielded HPGe has been controlled down to 5.2 cps/s within 60 keV~3 MeV region under the current low background environment. The activation platform of the SLEGS has provided favorable conditions for gamma activation measurements, which will play an important role in future research in the fields of nuclear physics, nuclear astrophysics, medical applications, materials science, and environmental science.
Shanghai Laser Electron Gamma Source (SLEGS) is a quasi-monoenergetic, and energy-tunable MeV gamma-rays source generated by the inverse Laser Compton Scattering (LCS) of lasers and electrons. SLEGS is the only LCS gamma source in the world with a continuously variable collision angular range. The gamma activation analysis is one of the effective methods to study the properties of materials. This paper introduces the gamma activation platform of SLEGS, including the online activation experiment, the low background offline measurement, and the energy and efficiency calibration for the high purity germanium (HPGe) detector. The counting rate of the shielded HPGe has been controlled down to 5.2 cps/s within 60 keV~3 MeV region under the current low background environment. The activation platform of the SLEGS has provided favorable conditions for gamma activation measurements, which will play an important role in future research in the fields of nuclear physics, nuclear astrophysics, medical applications, materials science, and environmental science.
2024, 41(1): 480-485.
doi: 10.11804/NuclPhysRev.41.2023CNPC06
Abstract:
Multi-Wire gaseous detectors have been widely used in the fields of nuclear physics and nuclear technology since they have the advantages of radiation hardness, fast response, large sensitive area, low cost and convenient fabrication. First, the electric field calculation theories for multi-wire gaseous detectors were introduced, and then the electric field calculations and the structure design for the drift region and avalanche region of a multi-wire gaseous detector had been carried out with ANSYS and GARFIELD. Next, the designed detector had been simulated in the case of cosmic ray irradiation with GEANT4, and the output results of current pulses, voltage pulses, the integrated charge for each event and the overall statistic results of the integrated charge were obtained. Furthermore, the multi-wire gaseous detector had been built and was used to measure the cosmic rays. The experiment results agree well with the previous simulation results. The simulation methods and the related experiment technologies in this study can be used to do design optimizations and experiment evaluations for gaseous detectors.
Multi-Wire gaseous detectors have been widely used in the fields of nuclear physics and nuclear technology since they have the advantages of radiation hardness, fast response, large sensitive area, low cost and convenient fabrication. First, the electric field calculation theories for multi-wire gaseous detectors were introduced, and then the electric field calculations and the structure design for the drift region and avalanche region of a multi-wire gaseous detector had been carried out with ANSYS and GARFIELD. Next, the designed detector had been simulated in the case of cosmic ray irradiation with GEANT4, and the output results of current pulses, voltage pulses, the integrated charge for each event and the overall statistic results of the integrated charge were obtained. Furthermore, the multi-wire gaseous detector had been built and was used to measure the cosmic rays. The experiment results agree well with the previous simulation results. The simulation methods and the related experiment technologies in this study can be used to do design optimizations and experiment evaluations for gaseous detectors.
2024, 41(1): 486-490.
doi: 10.11804/NuclPhysRev.41.2023CNPC08
Abstract:
Schottky diodes are fabricated using 100 µm thick 4H-SiC epitaxial wafers with Ohmic and Schottky contacts, and packaged as SiC detectors to meet the requirements of high temperature and radiation environments. The current-voltage (I-V) curves are measured in the range of 25 to 150 ºC. The experimental results show that the leakage current changes very little when the temperature is less than or equal to 105 ºC. The change rate of leakage current is 0.33%/ºC, when the reverse bias is −500 V and the temperature rises from 25 to 105 ºC. The SiC detector is irradiated by 60Co source in Peking University. The I-V characteristics of the SiC detector are compared before and after the irradiation experiment with total dose of 1 Mrad. The experimental data indicates that the leakage current has almost no significant change.
Schottky diodes are fabricated using 100 µm thick 4H-SiC epitaxial wafers with Ohmic and Schottky contacts, and packaged as SiC detectors to meet the requirements of high temperature and radiation environments. The current-voltage (I-V) curves are measured in the range of 25 to 150 ºC. The experimental results show that the leakage current changes very little when the temperature is less than or equal to 105 ºC. The change rate of leakage current is 0.33%/ºC, when the reverse bias is −500 V and the temperature rises from 25 to 105 ºC. The SiC detector is irradiated by 60Co source in Peking University. The I-V characteristics of the SiC detector are compared before and after the irradiation experiment with total dose of 1 Mrad. The experimental data indicates that the leakage current has almost no significant change.
2024, 41(1): 491-497.
doi: 10.11804/NuclPhysRev.41.2023CNPC03
Abstract:
The diamond-like carbon(DLC) stripper foils with ~5 μg/cm2 in thickness were produced by using the composite technology of the filtered cathodic vacuum arc(FCVA)- alternating current carbon arc(ACCA)-relaxation technique. The uniformity of the DLC foils were measured by the XP2U balance. The results show that the maximum inhomongeneity of DLC foils in the range of Φ100 mm is 8.82%. The microstructure of the DLC foils were measured by the scanning electron microscopy(SEM), Raman spectroscopy and X-ray photoelectron spectroscopy(XPS). The SEM images show that the DLC foils are smooth, and contain hardly droplets through the double 90° filters. The Raman spectrum indicates that the DLC foils are amorphous carbon films. The X-ray photoelectron spectrum indicates the sp3 bonds of the DLC foils exceed 70%. The irradiation lifetimes of the DLC stripper foils were tested with the heavy ion beams at the Beijing HI-13 Tandem Accelerator. The results indicate that the lifetime of the DLC stripper foils after relaxation is ~3 times of the DLC stripper foils before relaxation. The lifetime of DLC stripper foil is respectively 4 and 13 times of the carbon stripper foil for the 197Au− and 63Cu− ion beams(~9 MV, ~1 μA). The lifetime of DLC stripper foil is 2.6~10.0 times of the carbon stripper foil for the 107Ag−、70Ge−、48Ti−、28Si− and 127I− ion beams. The heavier ions and the stronger beam current, the longer lifetime of DLC stripper foil compared with that of carbon stripper foil. The lifetime of the DLC stripper foils is related to the substrate bias voltage, and increases at first and then decreases with the increasing of the substrate bias voltage. The lifetime reaches the peak value when the substrate bias voltage is −400 V.
The diamond-like carbon(DLC) stripper foils with ~5 μg/cm2 in thickness were produced by using the composite technology of the filtered cathodic vacuum arc(FCVA)- alternating current carbon arc(ACCA)-relaxation technique. The uniformity of the DLC foils were measured by the XP2U balance. The results show that the maximum inhomongeneity of DLC foils in the range of Φ100 mm is 8.82%. The microstructure of the DLC foils were measured by the scanning electron microscopy(SEM), Raman spectroscopy and X-ray photoelectron spectroscopy(XPS). The SEM images show that the DLC foils are smooth, and contain hardly droplets through the double 90° filters. The Raman spectrum indicates that the DLC foils are amorphous carbon films. The X-ray photoelectron spectrum indicates the sp3 bonds of the DLC foils exceed 70%. The irradiation lifetimes of the DLC stripper foils were tested with the heavy ion beams at the Beijing HI-13 Tandem Accelerator. The results indicate that the lifetime of the DLC stripper foils after relaxation is ~3 times of the DLC stripper foils before relaxation. The lifetime of DLC stripper foil is respectively 4 and 13 times of the carbon stripper foil for the 197Au− and 63Cu− ion beams(~9 MV, ~1 μA). The lifetime of DLC stripper foil is 2.6~10.0 times of the carbon stripper foil for the 107Ag−、70Ge−、48Ti−、28Si− and 127I− ion beams. The heavier ions and the stronger beam current, the longer lifetime of DLC stripper foil compared with that of carbon stripper foil. The lifetime of the DLC stripper foils is related to the substrate bias voltage, and increases at first and then decreases with the increasing of the substrate bias voltage. The lifetime reaches the peak value when the substrate bias voltage is −400 V.
2024, 41(1): 504-509.
doi: 10.11804/NuclPhysRev.41.2023CNPC72
Abstract:
This study establishes a novel high-resolution fast magnetic resonance imaging(MRI) method that incorporates Beam Eye View(BEV) and Beam Path View(BPV) fusion information. Three liver metastasis patients undergoing MRI guided radiotherapy(MRgRT) were selected. A total of 31 200 frames of MRI images were acquired from each patient using two motion patterns: restricted abdominal motion using an abdominal compression belt(RAM group) and free breathing(FB group). Tumor tracking was performed using nearby vessels with clear boundaries, and the radial vector motion amplitude difference(∆R95) within the 95% confidence interval was calculated. The differences in ΔR95 between the RAM and FB groups in all fractions on the BEV/BPV plane were as follows: for Patient 1, they were all less than 0.58 mm; for Patient 2, they were greater than 2.57 mm; for Patient 3, they were 0.71 and 1.05 mm, respectively. The results indicate that the abdominal compression technique can effectively reduce tumor motion magnitude, and the tumor motion magnitude ΔR95 variation is highly individual-specific. This method can serve as an imaging basis for the tumor margin reduction in MRgRT.
This study establishes a novel high-resolution fast magnetic resonance imaging(MRI) method that incorporates Beam Eye View(BEV) and Beam Path View(BPV) fusion information. Three liver metastasis patients undergoing MRI guided radiotherapy(MRgRT) were selected. A total of 31 200 frames of MRI images were acquired from each patient using two motion patterns: restricted abdominal motion using an abdominal compression belt(RAM group) and free breathing(FB group). Tumor tracking was performed using nearby vessels with clear boundaries, and the radial vector motion amplitude difference(∆R95) within the 95% confidence interval was calculated. The differences in ΔR95 between the RAM and FB groups in all fractions on the BEV/BPV plane were as follows: for Patient 1, they were all less than 0.58 mm; for Patient 2, they were greater than 2.57 mm; for Patient 3, they were 0.71 and 1.05 mm, respectively. The results indicate that the abdominal compression technique can effectively reduce tumor motion magnitude, and the tumor motion magnitude ΔR95 variation is highly individual-specific. This method can serve as an imaging basis for the tumor margin reduction in MRgRT.
2024, 41(1): 418-425.
doi: 10.11804/NuclPhysRev.41.2023CNPC70
Abstract:
Targeting the requirements of on-site high-energy non-destructive testing on modern aviation engine turbine blades and other military and basic heavy industry products, the accelerator research team at Xihua University has independently designed and developed a core device, the X-band 2 MeV small focus accelerator tube, working with X-band miniaturization accelerator technology. They have also integrated and developed a movable X-band 2 MeV small focus accelerator radiation device. The device integrates several subsystems, including X-band small focus standing wave accelerator tube, magnetron, microwave transmission system, accelerator head made of vacuum system and shielding body, high-voltage pulse modulator, control system, and cooling system. Among them, the small focus acceleration tube adopts a standing wave electric coupling structure, with a length of less than 100 mm, an output energy of 2 MeV, a focus size of less than 0.7 mm, and a dose rate of greater than 40 cGy/min at 1 m. After the successful development of the X-band 2 MeV small focus accelerator, a movable 2 MeV small focus CT system was built based on the device, and the system performance was tested and applied. As a result, the obtained image spatial resolution was significantly better than that of similar S-band high-energy CT products.
Targeting the requirements of on-site high-energy non-destructive testing on modern aviation engine turbine blades and other military and basic heavy industry products, the accelerator research team at Xihua University has independently designed and developed a core device, the X-band 2 MeV small focus accelerator tube, working with X-band miniaturization accelerator technology. They have also integrated and developed a movable X-band 2 MeV small focus accelerator radiation device. The device integrates several subsystems, including X-band small focus standing wave accelerator tube, magnetron, microwave transmission system, accelerator head made of vacuum system and shielding body, high-voltage pulse modulator, control system, and cooling system. Among them, the small focus acceleration tube adopts a standing wave electric coupling structure, with a length of less than 100 mm, an output energy of 2 MeV, a focus size of less than 0.7 mm, and a dose rate of greater than 40 cGy/min at 1 m. After the successful development of the X-band 2 MeV small focus accelerator, a movable 2 MeV small focus CT system was built based on the device, and the system performance was tested and applied. As a result, the obtained image spatial resolution was significantly better than that of similar S-band high-energy CT products.
2024, 41(1): 426-432.
doi: 10.11804/NuclPhysRev.41.2023CNPC86
Abstract:
With the technology improvement, a compact Accelerator Mass Spectrometry (AMS) device has been developed by China Institute of Atomic Energy on the basis of the low-energy AMS device developed earlier. The measurement method of 239Pu was investigated with newly established compact AMS device. In order to establish the 239Pu transport with the AMS system, the relationships of the transmission efficiency with the type of stripping gas, the selection of charge states, the thickness of stripping gas and the pre-acceleration voltage were systematically studied by using 238U, and then the optimized conditions of 239Pu measurement with the AMS system is established. It is verified that the linear R2 of the device is 0.999 7 and the detection limit of 239Pu is 0.1 fg through a series of standard samples and blank samples. It lays a foundation for the wide application of 239Pu in environmental and geological fields.
With the technology improvement, a compact Accelerator Mass Spectrometry (AMS) device has been developed by China Institute of Atomic Energy on the basis of the low-energy AMS device developed earlier. The measurement method of 239Pu was investigated with newly established compact AMS device. In order to establish the 239Pu transport with the AMS system, the relationships of the transmission efficiency with the type of stripping gas, the selection of charge states, the thickness of stripping gas and the pre-acceleration voltage were systematically studied by using 238U, and then the optimized conditions of 239Pu measurement with the AMS system is established. It is verified that the linear R2 of the device is 0.999 7 and the detection limit of 239Pu is 0.1 fg through a series of standard samples and blank samples. It lays a foundation for the wide application of 239Pu in environmental and geological fields.
2024, 41(1): 439-444.
doi: 10.11804/NuclPhysRev.41.2023CNPC47
Abstract:
Study of the exotic structure of nuclei in the neutron drip line region using radioactive ion beams and large neutron detector arrays is one of the current frontiers of nuclear physics research. As a key equipment for this study, the Advanced Multi-neutron Detection Array (AMDA) with high resolution and high efficiency is now under development. A prototype array has been built, which is composed of four test units each consisting of the BC408 plastic scintillator and SiPM. Its performance has been evaluated in the cosmic ray irradiation test. A time resolution of 167 ps and a position resolution of 1.69 cm were obtained, and the attenuation length was also determined. The good performance of the prototype has been demonstrated, which validates the technical design of AMDA.
Study of the exotic structure of nuclei in the neutron drip line region using radioactive ion beams and large neutron detector arrays is one of the current frontiers of nuclear physics research. As a key equipment for this study, the Advanced Multi-neutron Detection Array (AMDA) with high resolution and high efficiency is now under development. A prototype array has been built, which is composed of four test units each consisting of the BC408 plastic scintillator and SiPM. Its performance has been evaluated in the cosmic ray irradiation test. A time resolution of 167 ps and a position resolution of 1.69 cm were obtained, and the attenuation length was also determined. The good performance of the prototype has been demonstrated, which validates the technical design of AMDA.
2024, 41(1): 445-452.
doi: 10.11804/NuclPhysRev.41.2023CNPC58
Abstract:
In radioactive nuclear beam physical experiments with middle and low incident energies, the CsI(Tl) detectors are usually combined with the silicon detectors to make up of the Si-CsI(Tl) telescopes to identify charged particles using the $\varDelta E {\text{-}} E$ method. The performance of CsI(Tl) detector and the particle identification property of Si-CsI(Tl) telescope depend on the light output amount, light-output uniformity, as well as data acquisition system (DAQ). In this paper, we try to change the covering materials and the photon-electron conversion devices of the CsI(Tl) detector to increase the light output, improve the detection long-term stability and the light output uniformity of the wedged CsI(Tl) detector. Moreover, we test and compare the properties of Cs(Tl) detectors using different DAQ systems, which show that the energy resolution and the counting effective are better if the digital DAQ with the best parameters set is used for the Cs(Tl) detector.
In radioactive nuclear beam physical experiments with middle and low incident energies, the CsI(Tl) detectors are usually combined with the silicon detectors to make up of the Si-CsI(Tl) telescopes to identify charged particles using the $\varDelta E {\text{-}} E$ method. The performance of CsI(Tl) detector and the particle identification property of Si-CsI(Tl) telescope depend on the light output amount, light-output uniformity, as well as data acquisition system (DAQ). In this paper, we try to change the covering materials and the photon-electron conversion devices of the CsI(Tl) detector to increase the light output, improve the detection long-term stability and the light output uniformity of the wedged CsI(Tl) detector. Moreover, we test and compare the properties of Cs(Tl) detectors using different DAQ systems, which show that the energy resolution and the counting effective are better if the digital DAQ with the best parameters set is used for the Cs(Tl) detector.
2024, 41(1): 453-459.
doi: 10.11804/NuclPhysRev.41.2023CNPC61
Abstract:
Cosmic rays are used for the calibration of the Veto detector at ETF (External Target Facility) in HIRFL-CSR (Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou). The work primarily involves two parts: position calibration and time calibration. Position calibration can provide the precise location of particle hits on the Veto detector, while time calibration can establish a uniform standard for the detection of the moment when a particle hits the detector. The information of hit position and hit time is crucial for identifying and excluding events of charged particles incident on the neutron wall detector, providing important support for the achievement of the physical objectives of the neutron wall detector. During the calibration process, the Veto detector's position resolution FWHM (Full Width at Half Maximum), was determined to be 2.53 cm, and the time resolution FWHM, after the normalization of the times of all unit bars, was found to be 1.09 ns.
Cosmic rays are used for the calibration of the Veto detector at ETF (External Target Facility) in HIRFL-CSR (Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou). The work primarily involves two parts: position calibration and time calibration. Position calibration can provide the precise location of particle hits on the Veto detector, while time calibration can establish a uniform standard for the detection of the moment when a particle hits the detector. The information of hit position and hit time is crucial for identifying and excluding events of charged particles incident on the neutron wall detector, providing important support for the achievement of the physical objectives of the neutron wall detector. During the calibration process, the Veto detector's position resolution FWHM (Full Width at Half Maximum), was determined to be 2.53 cm, and the time resolution FWHM, after the normalization of the times of all unit bars, was found to be 1.09 ns.
2024, 41(1): 460-466.
doi: 10.11804/NuclPhysRev.41.2023CNPC76
Abstract:
HFRS (High energy FRagment Separator), an advanced in-flight radioactive separator at HIAF (High Intensity heavy ion Accelerator Facility), which is a new accelerator facility under construction in China, will provide promising opportunities for the high-energy radioactive beam physics research. The beam intensity of HFRS is extremely high ($1\times {{10}^{11}}$ ppp for the primary beam), so that the energy loss measurement detectors used for particles identification should be able to operate at very high counting rate. However, the conventional energy loss detectors suffer from slow electronics response, severe pulse pile-up, and it is difficult to operate at high counting rate. In this paper, we propose a method to measure the energy loss at higher counting rate. We use a radiation-resistant multiple sampling ionization chamber as the energy loss measurement detector, and optimize the detector structure and readout methods to enhance detector response speed, then employ fast charge-sensitive preamplifiers for preliminary signal amplification, directly sample the pulse waveforms with a waveform digitizer. Finally, better performance can be obtained with subsequent digital algorithms. The method was validated and tested using both radioactive sources and beams. During the test with a compound components α source, a good energy resolution (FWHM) of 1.31% was achieved. During the test with a ${}^{56}{\rm{Fe}}$ beam (300 MeV/u) provided by RIBLL2 (the second Radioactive Ion Beam Line in Lanzhou), no significant pulse pile-up was found at high counting rate even close to 1MHz, when a suitable time constant (${{\tau }_{\rm{f}}}=2 \; \mu {\rm{s}}$) of the preamplifier was set.
HFRS (High energy FRagment Separator), an advanced in-flight radioactive separator at HIAF (High Intensity heavy ion Accelerator Facility), which is a new accelerator facility under construction in China, will provide promising opportunities for the high-energy radioactive beam physics research. The beam intensity of HFRS is extremely high ($1\times {{10}^{11}}$ ppp for the primary beam), so that the energy loss measurement detectors used for particles identification should be able to operate at very high counting rate. However, the conventional energy loss detectors suffer from slow electronics response, severe pulse pile-up, and it is difficult to operate at high counting rate. In this paper, we propose a method to measure the energy loss at higher counting rate. We use a radiation-resistant multiple sampling ionization chamber as the energy loss measurement detector, and optimize the detector structure and readout methods to enhance detector response speed, then employ fast charge-sensitive preamplifiers for preliminary signal amplification, directly sample the pulse waveforms with a waveform digitizer. Finally, better performance can be obtained with subsequent digital algorithms. The method was validated and tested using both radioactive sources and beams. During the test with a compound components α source, a good energy resolution (FWHM) of 1.31% was achieved. During the test with a ${}^{56}{\rm{Fe}}$ beam (300 MeV/u) provided by RIBLL2 (the second Radioactive Ion Beam Line in Lanzhou), no significant pulse pile-up was found at high counting rate even close to 1MHz, when a suitable time constant (${{\tau }_{\rm{f}}}=2 \; \mu {\rm{s}}$) of the preamplifier was set.
2024, 41(1): 467-472.
doi: 10.11804/NuclPhysRev.41.2023CNPC67
Abstract:
The β-Oslo experimental method provides an important investigative tool for examining the properties of radioactive nuclides in highly excited states and exploring the nucleosynthesis process for elements ranging from iron to uranium. This paper introduces a novel data processing technique designed to eliminate the impact of β-decay electrons on the detection of nuclear γ de-excitation within β-Oslo experiments, accurately unfolding the observed γ-ray spectra. Utilizing a comprehensive detector response function matrix for γ rays and decay electrons, this method combines column-pivotal elimination and iterative step-by-step inverse solution approaches to determine the true incident γ spectrum. The reliability and validity of the proposed method have been substantiated through extensive simulations and inverse calculations.
The β-Oslo experimental method provides an important investigative tool for examining the properties of radioactive nuclides in highly excited states and exploring the nucleosynthesis process for elements ranging from iron to uranium. This paper introduces a novel data processing technique designed to eliminate the impact of β-decay electrons on the detection of nuclear γ de-excitation within β-Oslo experiments, accurately unfolding the observed γ-ray spectra. Utilizing a comprehensive detector response function matrix for γ rays and decay electrons, this method combines column-pivotal elimination and iterative step-by-step inverse solution approaches to determine the true incident γ spectrum. The reliability and validity of the proposed method have been substantiated through extensive simulations and inverse calculations.
2024, 41(1): 473-479.
doi: 10.11804/NuclPhysRev.41.2023CNPC69
Abstract:
Charge exchange reactions with the intermediate energy can be used to study the complex structure of atomic nuclei from the respect of spin-isospin excitation. By utilizing the radioactive beam line at the Institute of Modern Physics, Chinese Academy of Sciences, charge exchange reaction experiments in inverse kinematics can expand the target nuclides to be studied to neutron-rich nuclei and even unstable nuclei. Based on this, a detector system for charge exchange reaction experiments has been designed, which mainly consists of a 3He gas target, TPC and CsI(Tl) arrays, where the TPC and CsI(Tl) arrays form a ΔE-E system. Using simulation software such as Geant4 and Garfield++, the operating conditions of the TPC were optimized, the kinematic intervals and the basic design of the detector for the experimental study were determined, and the particle discrimination ability of the detection system was investigated. Based on the simulation, the detection system was built and the spatial resolution of the TPC was measured by using the UV laser. On the readout electrode plane, the resolution is about 422 μm. And the resolution is about 681 μm in the drift direction. The performance of the TPC is sufficient to support the track reconstruction of the secondary particles of the nuclear reaction, and in particular, it is able to achieve a high resolution of the scattering angle.
Charge exchange reactions with the intermediate energy can be used to study the complex structure of atomic nuclei from the respect of spin-isospin excitation. By utilizing the radioactive beam line at the Institute of Modern Physics, Chinese Academy of Sciences, charge exchange reaction experiments in inverse kinematics can expand the target nuclides to be studied to neutron-rich nuclei and even unstable nuclei. Based on this, a detector system for charge exchange reaction experiments has been designed, which mainly consists of a 3He gas target, TPC and CsI(Tl) arrays, where the TPC and CsI(Tl) arrays form a ΔE-E system. Using simulation software such as Geant4 and Garfield++, the operating conditions of the TPC were optimized, the kinematic intervals and the basic design of the detector for the experimental study were determined, and the particle discrimination ability of the detection system was investigated. Based on the simulation, the detection system was built and the spatial resolution of the TPC was measured by using the UV laser. On the readout electrode plane, the resolution is about 422 μm. And the resolution is about 681 μm in the drift direction. The performance of the TPC is sufficient to support the track reconstruction of the secondary particles of the nuclear reaction, and in particular, it is able to achieve a high resolution of the scattering angle.
2024, 41(1): 498-503.
doi: 10.11804/NuclPhysRev.41.2023CNPC66
Abstract:
Room-temperature ferromagnetism is observed in the O+-implanted AlN films with O+ doses of ${5\times10^{16}}$ cm−2 (AlN:$ {\rm{O}}_{5\times10^{16}} $) and ${2\times10^{17}}$ cm−2 (AlN:$ {\rm{O}}_{2\times10^{17}} $). The observed magnetic anisotropy indicates that the ferromagnetism is attributed to the intrinsic properties of O+-implanted AlN films. The out-of-plane saturation magnetization ($M_{\rm{S}}$) of the AlN:$ {\rm{O}}_{5\times10^{16}}$ is about 0.68 emu/g, much higher than that of AlN:$ {\rm{O}}_{2\times10^{17}} $, 0.09 emu/g, which is due to the excessively high O+ dose made more O+ ions occupy adjacent Al3+ positions in forms of antiferromagnetic coupling. Doppler broadening of positron annihilation radiation measurements demonstrate the existence of Al vacancies in the O+-implanted AlN films. The first-principles calculations suggest that the ferromagnetism originates mainly from the Al vacancies. Meanwhile, the formation of divacancies or vacancy clusters by high concentrations of Al vacancies will lead to the transformation of VAl–VAl coupling from ferromagnetim to antiferromagnetism, ultimately weakening the ferromagnetism of the sample.
Room-temperature ferromagnetism is observed in the O+-implanted AlN films with O+ doses of ${5\times10^{16}}$ cm−2 (AlN:$ {\rm{O}}_{5\times10^{16}} $) and ${2\times10^{17}}$ cm−2 (AlN:$ {\rm{O}}_{2\times10^{17}} $). The observed magnetic anisotropy indicates that the ferromagnetism is attributed to the intrinsic properties of O+-implanted AlN films. The out-of-plane saturation magnetization ($M_{\rm{S}}$) of the AlN:$ {\rm{O}}_{5\times10^{16}}$ is about 0.68 emu/g, much higher than that of AlN:$ {\rm{O}}_{2\times10^{17}} $, 0.09 emu/g, which is due to the excessively high O+ dose made more O+ ions occupy adjacent Al3+ positions in forms of antiferromagnetic coupling. Doppler broadening of positron annihilation radiation measurements demonstrate the existence of Al vacancies in the O+-implanted AlN films. The first-principles calculations suggest that the ferromagnetism originates mainly from the Al vacancies. Meanwhile, the formation of divacancies or vacancy clusters by high concentrations of Al vacancies will lead to the transformation of VAl–VAl coupling from ferromagnetim to antiferromagnetism, ultimately weakening the ferromagnetism of the sample.
2024, 41(1): 510-514.
doi: 10.11804/NuclPhysRev.41.2023CNPC18
Abstract:
The nucleon-nucleon short-range correlation(NN-SRC) is one of the key issues in nuclear physics that cause high-momentum tails in the nucleon momentum distributions. In this paper, the nuclear spectral functions are constructed based on the axially deformed relativistic mean-field model, and the correction of the short-range correlation effect is introduced. Then, the inclusive scattering cross sections are calculated using the nuclear spectral function and the framework of the plane wave impulse approximation, including both the quasielastic and Δ resonance parts. In particular, in the Δ resonance region, the electromagnetic structure of the nucleon resonance state Δ(1232) is reconsidered, which effectively improves the theoretical calculations that can be in better agreement with experimental data. The paper further divides the inclusive scattering cross sections into the contributions of NN-SRC and mean-field. It is found that, the quasielastic peak and Δ resonance peak not only reflect the mean-field structure but also are sensitive to NN-SRC information. Finally, we propose a method for extracting the NN-SRC strength of nuclei from experimental cross-section data.
The nucleon-nucleon short-range correlation(NN-SRC) is one of the key issues in nuclear physics that cause high-momentum tails in the nucleon momentum distributions. In this paper, the nuclear spectral functions are constructed based on the axially deformed relativistic mean-field model, and the correction of the short-range correlation effect is introduced. Then, the inclusive scattering cross sections are calculated using the nuclear spectral function and the framework of the plane wave impulse approximation, including both the quasielastic and Δ resonance parts. In particular, in the Δ resonance region, the electromagnetic structure of the nucleon resonance state Δ(1232) is reconsidered, which effectively improves the theoretical calculations that can be in better agreement with experimental data. The paper further divides the inclusive scattering cross sections into the contributions of NN-SRC and mean-field. It is found that, the quasielastic peak and Δ resonance peak not only reflect the mean-field structure but also are sensitive to NN-SRC information. Finally, we propose a method for extracting the NN-SRC strength of nuclei from experimental cross-section data.
2024, 41(1): 515-521.
doi: 10.11804/NuclPhysRev.41.2023CNPC78
Abstract:
Within the framework of Lanzhou quantum molecular dynamics (LQMD) transport model, we investigate the particle production and fragmentation mechanism of target nucleus induced by antiproton with the Skyrme energy density functional and relativistic covariant density functional, respectively. The temporal evolution and phase-space distributions of π, K, Λ and Σ as well as the mass and charge distributions of nuclear fragments and hypernuclear fragments are analyzed by the model in the reaction of antiproton on $^{58}{\mathrm{Ni}}$ at an incident momentum of 5 GeV/c. It is found that the phase-space distributions of particles are similar with the two mean-field potentials, but different situation for the fragment distribution, in particular for the intermediate mass fragments. The fluctuation effect of the collision system is more obvious under the relativistic mean field, which leads to the high debris yield.
Within the framework of Lanzhou quantum molecular dynamics (LQMD) transport model, we investigate the particle production and fragmentation mechanism of target nucleus induced by antiproton with the Skyrme energy density functional and relativistic covariant density functional, respectively. The temporal evolution and phase-space distributions of π, K, Λ and Σ as well as the mass and charge distributions of nuclear fragments and hypernuclear fragments are analyzed by the model in the reaction of antiproton on $^{58}{\mathrm{Ni}}$ at an incident momentum of 5 GeV/c. It is found that the phase-space distributions of particles are similar with the two mean-field potentials, but different situation for the fragment distribution, in particular for the intermediate mass fragments. The fluctuation effect of the collision system is more obvious under the relativistic mean field, which leads to the high debris yield.
2024, 41(1): 522-529.
doi: 10.11804/NuclPhysRev.41.2023CNPC16
Abstract:
The investigation of the equation of state(EoS) of nuclear matter, especially at high baryon densities is one of the hot topics in the frontier of nuclear physics. The impact of the EoS at 2~5 times saturation density $\rho_{0}$ on the two-particle correlation is discussed with the ultra-relativistic quantum molecular dynamics(UrQMD) model. Focusing on the two π Hanbury-Brown-Twiss(HBT) correlations, by adopting different EoSs, the effects of potential interaction and phase transition on the HBT correlation and the spatiotemporal properties of the emission source of π are investigated. The results show that below $\sim5 \rho_{0}$, the HBT radius and parameters are sensitive to the stiffness of the EoS. By comparing with the experiment data, first-order phase transition with a significant softening of the equation of state below 4 times nuclear saturation density can be excluded using HBT data, and the available data on the HBT radii in the investigated energy region favor a relatively stiff EoS at low densities, which then turns into a soft EoS at high densities. These results highlight that the pion's HBT radius and parameters are sensitive to the stiffness of the equation of state, and can be used to constrain and understand the equation of state in the high baryon density region.
The investigation of the equation of state(EoS) of nuclear matter, especially at high baryon densities is one of the hot topics in the frontier of nuclear physics. The impact of the EoS at 2~5 times saturation density $\rho_{0}$ on the two-particle correlation is discussed with the ultra-relativistic quantum molecular dynamics(UrQMD) model. Focusing on the two π Hanbury-Brown-Twiss(HBT) correlations, by adopting different EoSs, the effects of potential interaction and phase transition on the HBT correlation and the spatiotemporal properties of the emission source of π are investigated. The results show that below $\sim5 \rho_{0}$, the HBT radius and parameters are sensitive to the stiffness of the EoS. By comparing with the experiment data, first-order phase transition with a significant softening of the equation of state below 4 times nuclear saturation density can be excluded using HBT data, and the available data on the HBT radii in the investigated energy region favor a relatively stiff EoS at low densities, which then turns into a soft EoS at high densities. These results highlight that the pion's HBT radius and parameters are sensitive to the stiffness of the equation of state, and can be used to constrain and understand the equation of state in the high baryon density region.
2024, 41(1): 530-535.
doi: 10.11804/NuclPhysRev.41.2023CNPC19
Abstract:
The number of constituent quark(NCQ) scaling of elliptic flow in heavy-ion collisions is one of the important signals of parton anisotropic degrees of freedom. In this work, we systematically study the $\upsilon_{2}^{}$ of light flavor hadrons as well as its NCQ scaling in p−Pb collisions at 5.02 TeV, with a multiphase transport(AMPT) model. Based on the advanced flow extraction method, the AMPT model calculations provide a good description of the measured transverse momentum($p_{\mathrm{T}}^{}$)-differential $\upsilon_{2}^{}$ of mesons but exhibit a slight deviation of the baryon $\upsilon_{2}^{}$. We find that the NCQ scaling is mainly driven by the combination of parton cascade and quark recombination, and also affected by the nonflow contribution and hardronic rescattering. This study provides new insights into understanding the origin of collective-like behaviors in small collision system.
The number of constituent quark(NCQ) scaling of elliptic flow in heavy-ion collisions is one of the important signals of parton anisotropic degrees of freedom. In this work, we systematically study the $\upsilon_{2}^{}$ of light flavor hadrons as well as its NCQ scaling in p−Pb collisions at 5.02 TeV, with a multiphase transport(AMPT) model. Based on the advanced flow extraction method, the AMPT model calculations provide a good description of the measured transverse momentum($p_{\mathrm{T}}^{}$)-differential $\upsilon_{2}^{}$ of mesons but exhibit a slight deviation of the baryon $\upsilon_{2}^{}$. We find that the NCQ scaling is mainly driven by the combination of parton cascade and quark recombination, and also affected by the nonflow contribution and hardronic rescattering. This study provides new insights into understanding the origin of collective-like behaviors in small collision system.
2024, 41(1): 536-544.
doi: 10.11804/NuclPhysRev.41.2023CNPC17
Abstract:
In heavy ion collisions(HICs), the production of light particles plays an important role in extracting information about the equation of state(EoS) of nuclear matter. Based on the Ultra-relativistic Quantum Molecular Dynamics(UrQMD) model, the effect of the sequential decay on the collective flows and the nuclear stopping power of light particles in Au+Au collisions at intermediate energies were investigated, with the statistical decay model GEMINI++ is used to process the secondary decay of the primary fragments. It is found that due to the memory effect and the daughter nuclei produced by decay inherent part of the dynamic information of the parent nucleus, the experimental data can be better described by considering the sequential decay. And the influence of the sequential decay on the observables weakens with the increase of the collision energy. The results highlight that the sequential decay and the production of light particles in HICs have an obvious effect on the observables sensitive to the EoS, and these effects should be considered when adopting these observables to extract the information of the EoS.
In heavy ion collisions(HICs), the production of light particles plays an important role in extracting information about the equation of state(EoS) of nuclear matter. Based on the Ultra-relativistic Quantum Molecular Dynamics(UrQMD) model, the effect of the sequential decay on the collective flows and the nuclear stopping power of light particles in Au+Au collisions at intermediate energies were investigated, with the statistical decay model GEMINI++ is used to process the secondary decay of the primary fragments. It is found that due to the memory effect and the daughter nuclei produced by decay inherent part of the dynamic information of the parent nucleus, the experimental data can be better described by considering the sequential decay. And the influence of the sequential decay on the observables weakens with the increase of the collision energy. The results highlight that the sequential decay and the production of light particles in HICs have an obvious effect on the observables sensitive to the EoS, and these effects should be considered when adopting these observables to extract the information of the EoS.
2024, 41(1): 545-550.
doi: 10.11804/NuclPhysRev.41.2023CNPC24
Abstract:
Based on the self-consistent RBUU transport theory, the isospin-dependent in-medium $ {\rm{N}} \Delta \rightarrow {\rm{N}} \Delta$ cross section is investigated. It is found that the isospin effect has a relatively obvious influence on the effective mass of baryons and the total $ {\rm{N}} \Delta $ elastic cross section in different density regions. With the increase of baryon density, the effective mass splitting between different isospin states of baryons increases gradually. Under the joint effect of density-dependent baryon effective mass splitting, coupling constant, as well as Born terms such as $\sigma-\delta$, $\sigma-\rho$, $\omega-\delta$, $\omega-\rho$, the elastic cross-sections of sub-channels with different isospin states exhibit different density-dependent behaviors. The total cross-section has an obvious reduction effect of medium in the low-energy region, and the medium effect is weakened in the high-energy region.
Based on the self-consistent RBUU transport theory, the isospin-dependent in-medium $ {\rm{N}} \Delta \rightarrow {\rm{N}} \Delta$ cross section is investigated. It is found that the isospin effect has a relatively obvious influence on the effective mass of baryons and the total $ {\rm{N}} \Delta $ elastic cross section in different density regions. With the increase of baryon density, the effective mass splitting between different isospin states of baryons increases gradually. Under the joint effect of density-dependent baryon effective mass splitting, coupling constant, as well as Born terms such as $\sigma-\delta$, $\sigma-\rho$, $\omega-\delta$, $\omega-\rho$, the elastic cross-sections of sub-channels with different isospin states exhibit different density-dependent behaviors. The total cross-section has an obvious reduction effect of medium in the low-energy region, and the medium effect is weakened in the high-energy region.
2024, 41(1): 551-557.
doi: 10.11804/NuclPhysRev.41.2023CNPC25
Abstract:
Within the ultra-relativistic quantum molecular dynamics (UrQMD) model, the effect of initial density fluctuations, which caused by varying the minimum distance $d_{\min}^{}$ between two nucleons in the initialization, on cumulants of the net-proton multiplicity distribution in Au + Au collisions at $\sqrt{s_{\rm{NN}}^{}}$= 7.7 GeV is investigated. It is found that the density fluctuations in the initial state increase with the decrease of $d_{\min}^{}$ from 1.6 to 1.0 fm. During the expand of fireball, the effect of initial density fluctuations on cumulants gradually reduced, while the influence of mean-field is remarkable. In the momentum space of the final state of the collision, the influence of $d_{\min}^{}$ on the magnitude of the net-proton number fluctuation in a narrow pseudo-rapidity window ($\varDelta \eta \leqslant $ 4) is negligible. However, in a broad pseudo-rapidity window ($\varDelta \eta > 4$), $d_{\min}^{}$ obviously impacts the cumulant ratios of net-proton multiplicity. In the semi-center collision ($b$= 5 fm), the effect of $d_{\min}^{}$ is about 2~3 times than that of the mean-field.
Within the ultra-relativistic quantum molecular dynamics (UrQMD) model, the effect of initial density fluctuations, which caused by varying the minimum distance $d_{\min}^{}$ between two nucleons in the initialization, on cumulants of the net-proton multiplicity distribution in Au + Au collisions at $\sqrt{s_{\rm{NN}}^{}}$= 7.7 GeV is investigated. It is found that the density fluctuations in the initial state increase with the decrease of $d_{\min}^{}$ from 1.6 to 1.0 fm. During the expand of fireball, the effect of initial density fluctuations on cumulants gradually reduced, while the influence of mean-field is remarkable. In the momentum space of the final state of the collision, the influence of $d_{\min}^{}$ on the magnitude of the net-proton number fluctuation in a narrow pseudo-rapidity window ($\varDelta \eta \leqslant $ 4) is negligible. However, in a broad pseudo-rapidity window ($\varDelta \eta > 4$), $d_{\min}^{}$ obviously impacts the cumulant ratios of net-proton multiplicity. In the semi-center collision ($b$= 5 fm), the effect of $d_{\min}^{}$ is about 2~3 times than that of the mean-field.
2024, 41(1): 558-563.
doi: 10.11804/NuclPhysRev.41.2023CNPC14
Abstract:
There must be electromagnetic fields created during high-energy heavy-ion collisions. Although the electromagnetic field may become weak with the evolution of the quark-gluon plasma (QGP), compared to the energy scales of the strong interaction, they are potentially important to some electromagnetic probes. In this work, we propose the coupled effect of the weak magnetic field and the longitudinal dynamics of the background medium for the first time. We demonstrate that the induced photon spectrum can be highly azimuthally anisotropic when the quark-gluon plasma is in the presence of a weak external magnetic field. On the other hand, the weak magnetic photon emission from quark-gluon plasma only leads to a small correction to the photon production rate. After hydrodynamic evolution with a tilted fireball configuration, the experimentally measured direct photon elliptic flow is well reproduced. Meanwhile, the used time-averaged magnetic field in the hydrodynamic stage is found no larger than a few percent of the pion mass square.
There must be electromagnetic fields created during high-energy heavy-ion collisions. Although the electromagnetic field may become weak with the evolution of the quark-gluon plasma (QGP), compared to the energy scales of the strong interaction, they are potentially important to some electromagnetic probes. In this work, we propose the coupled effect of the weak magnetic field and the longitudinal dynamics of the background medium for the first time. We demonstrate that the induced photon spectrum can be highly azimuthally anisotropic when the quark-gluon plasma is in the presence of a weak external magnetic field. On the other hand, the weak magnetic photon emission from quark-gluon plasma only leads to a small correction to the photon production rate. After hydrodynamic evolution with a tilted fireball configuration, the experimentally measured direct photon elliptic flow is well reproduced. Meanwhile, the used time-averaged magnetic field in the hydrodynamic stage is found no larger than a few percent of the pion mass square.
2024, 41(1): 564-572.
doi: 10.11804/NuclPhysRev.41.2023CNPC15
Abstract:
In this work, the polarization effects of a strongly magnetized quark-gluon plasma are studied at finite temperature. It is found that a background magnetic field can have a strong effect on the photon and dilepton emission rates. It affects not only the total rate but also the angular dependence. In particular, the Landau-level quantization leads to a nontrivial momentum dependence of the photon/dilepton anisotropic flow coefficient on transverse momentum. In the case of photon emission, nonzero coefficients $\upsilon _n$ (with even n) have opposite signs at small and large values of the transverse momentum. Additionally, the $\upsilon _n$ signs alternate with increasing n, and their approximate values decrease as $1/n^2$ in magnitude. The anisotropy of dilepton emission is well-pronounced only at large transverse momenta and small invariant masses. The corresponding $\upsilon _n$ coefficients are of the same magnitude and show a similar sign-alternative pattern with increasing n as in the photon emission. It is proposed that the anisotropy of the photon and dilepton emission may serve as indirect measurements of the magnetic field.
In this work, the polarization effects of a strongly magnetized quark-gluon plasma are studied at finite temperature. It is found that a background magnetic field can have a strong effect on the photon and dilepton emission rates. It affects not only the total rate but also the angular dependence. In particular, the Landau-level quantization leads to a nontrivial momentum dependence of the photon/dilepton anisotropic flow coefficient on transverse momentum. In the case of photon emission, nonzero coefficients $\upsilon _n$ (with even n) have opposite signs at small and large values of the transverse momentum. Additionally, the $\upsilon _n$ signs alternate with increasing n, and their approximate values decrease as $1/n^2$ in magnitude. The anisotropy of dilepton emission is well-pronounced only at large transverse momenta and small invariant masses. The corresponding $\upsilon _n$ coefficients are of the same magnitude and show a similar sign-alternative pattern with increasing n as in the photon emission. It is proposed that the anisotropy of the photon and dilepton emission may serve as indirect measurements of the magnetic field.
2024, 41(1): 573-579.
doi: 10.11804/NuclPhysRev.41.2023CNPC46
Abstract:
The search for chiral magnetic effects (CME) in relativistic heavy-ion collisions helps us to understand CP symmetry breaking in strong interactions and the topological nature of the quantum chromodynamic (QCD) vacuum. A two-plane method was proposed based on the fact that the background and signal of CME have different correlations relative to the spectator plane and the participant plane. Using a multiphase transport model with different input strengths of CME, we revisit the two-plane method in isobar collisions at $\sqrt{s_{_{\rm NN}}} = 200 \;{\mathrm{GeV}}$. The relative correlations of the CME signal and background to two different planes were found to be different, which is inconsistent with the assumptions made in the current experimental measurements. The difference arises from the decorrelation of the CME relative to the spectator and participant planes, which originates from the final state interactions. Our finding suggests that the current experimental measurements may overestimate the fraction of the CME signal in the final state in relativistic heavy-ion collisions.
The search for chiral magnetic effects (CME) in relativistic heavy-ion collisions helps us to understand CP symmetry breaking in strong interactions and the topological nature of the quantum chromodynamic (QCD) vacuum. A two-plane method was proposed based on the fact that the background and signal of CME have different correlations relative to the spectator plane and the participant plane. Using a multiphase transport model with different input strengths of CME, we revisit the two-plane method in isobar collisions at $\sqrt{s_{_{\rm NN}}} = 200 \;{\mathrm{GeV}}$. The relative correlations of the CME signal and background to two different planes were found to be different, which is inconsistent with the assumptions made in the current experimental measurements. The difference arises from the decorrelation of the CME relative to the spectator and participant planes, which originates from the final state interactions. Our finding suggests that the current experimental measurements may overestimate the fraction of the CME signal in the final state in relativistic heavy-ion collisions.
2024, 41(1): 580-586.
doi: 10.11804/NuclPhysRev.41.2023CNPC52
Abstract:
One of the frontier research in high-energy nuclear physics is to study the Quantum Chromodynamics (QCD) phase diagram and locate the critical point. According to 3D Ising-QCD theory, critical intermittency is a distinctive feature of the QCD critical point, and thereby the measurement of intermittency can be served as a crucial probe for studying the QCD phase structure. This paper briefly review recent progress of intermittency analysis in relativistic heavy-ion collisions. In experiment, we present the results of charged hadrons in Au+Au collisions from the RHIC-STAR experiment, and proton results in Ar+Sc collisions from the SPS-NA61 experiment. Additionally, the results from the hybird UrQMD+CMC model are also introduced. Finally, we give a outlook for next stage of research.
One of the frontier research in high-energy nuclear physics is to study the Quantum Chromodynamics (QCD) phase diagram and locate the critical point. According to 3D Ising-QCD theory, critical intermittency is a distinctive feature of the QCD critical point, and thereby the measurement of intermittency can be served as a crucial probe for studying the QCD phase structure. This paper briefly review recent progress of intermittency analysis in relativistic heavy-ion collisions. In experiment, we present the results of charged hadrons in Au+Au collisions from the RHIC-STAR experiment, and proton results in Ar+Sc collisions from the SPS-NA61 experiment. Additionally, the results from the hybird UrQMD+CMC model are also introduced. Finally, we give a outlook for next stage of research.
2024, 41(1): 587-593.
doi: 10.11804/NuclPhysRev.41.2023CNPC29
Abstract:
The speed of sound in quark matter is an important physical quantity for studying the properties and the spacetime evolution of quark-gluon plasma (QGP). The behavior of the speed of sound with respect to temperature and density can reveal to some extent the equation of state and the phase structure of QGP. Building upon the previous studies on the speed of sound in symmetric quark matter, the formulae for calculating the speed of sound in asymmetric quark matter in the temperature-density space are further derived. The PNJL model is then used to calculate the dependence of the speed of sound on isospin asymmetry. Furthermore, the relationship between the magnitude of the speed of sound and the QCD phase structure is discussed, and the regions where the acoustic equation fails are indicated under different physical conditions. It is found that the boundary of vanishing sound speed in asymmetric quark matter is smaller than that in symmetric quark matter, meaning that the range where the acoustic wave equation fails in asymmetric quark matter is smaller than that in symmetric quark matter. The results also indicate that in most of the stable phase, the speed of sound in asymmetric quark matter is slightly larger than that in symmetric quark matter.
The speed of sound in quark matter is an important physical quantity for studying the properties and the spacetime evolution of quark-gluon plasma (QGP). The behavior of the speed of sound with respect to temperature and density can reveal to some extent the equation of state and the phase structure of QGP. Building upon the previous studies on the speed of sound in symmetric quark matter, the formulae for calculating the speed of sound in asymmetric quark matter in the temperature-density space are further derived. The PNJL model is then used to calculate the dependence of the speed of sound on isospin asymmetry. Furthermore, the relationship between the magnitude of the speed of sound and the QCD phase structure is discussed, and the regions where the acoustic equation fails are indicated under different physical conditions. It is found that the boundary of vanishing sound speed in asymmetric quark matter is smaller than that in symmetric quark matter, meaning that the range where the acoustic wave equation fails in asymmetric quark matter is smaller than that in symmetric quark matter. The results also indicate that in most of the stable phase, the speed of sound in asymmetric quark matter is slightly larger than that in symmetric quark matter.
2024, 41(1): 594-599.
doi: 10.11804/NuclPhysRev.41.2023CNPC02
Abstract:
In a high-temperature and high-density quark-gluon plasma (QGP), the thermal partons modify the heavy quark potential. It is widely accepted that the real part of the heavy quark potential should fall within the range of the free energy F and the internal energy U of heavy quarkonium, depending on the temperature. The imaginary part of the interaction potential of heavy quarkonium is derived from the Landau damping effect. In this study, we investigate the evolution of the wave function of heavy quarkonium in the QGP and calculate the nuclear modification factor of heavy quarkonium using the time-dependent Schrödinger equation model and different interaction potentials for heavy quarks. We simultaneously consider both the cold nuclear effects and the hot nuclear effects, and compare the theoretical calculations of the nuclear modification factor of bottomonium with experimental data. Our findings reveal that when the real part of the interaction potential of heavy quarkonium approaches the internal energy U, it can better explain the experimental phenomena. Additionally, we observe the phenomenon of sequential suppression of different bottomonium states, indicating that higher excited states of bottomonium are more easily dissociated due to their smaller binding energies. The Schrödinger equation model is a valuable tool for establishing a direct connection between the finite-temperature heavy quark potential and experimental observables, and for determining the form of the interaction potential.
In a high-temperature and high-density quark-gluon plasma (QGP), the thermal partons modify the heavy quark potential. It is widely accepted that the real part of the heavy quark potential should fall within the range of the free energy F and the internal energy U of heavy quarkonium, depending on the temperature. The imaginary part of the interaction potential of heavy quarkonium is derived from the Landau damping effect. In this study, we investigate the evolution of the wave function of heavy quarkonium in the QGP and calculate the nuclear modification factor of heavy quarkonium using the time-dependent Schrödinger equation model and different interaction potentials for heavy quarks. We simultaneously consider both the cold nuclear effects and the hot nuclear effects, and compare the theoretical calculations of the nuclear modification factor of bottomonium with experimental data. Our findings reveal that when the real part of the interaction potential of heavy quarkonium approaches the internal energy U, it can better explain the experimental phenomena. Additionally, we observe the phenomenon of sequential suppression of different bottomonium states, indicating that higher excited states of bottomonium are more easily dissociated due to their smaller binding energies. The Schrödinger equation model is a valuable tool for establishing a direct connection between the finite-temperature heavy quark potential and experimental observables, and for determining the form of the interaction potential.
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