2009年 第26卷 第S1期
We study the origin of baryon resonances which are dynamically generated in the chiral unitary approach. We propose a natural renormalization scheme for the dynamical generation of resonances using the low energy chiral interaction and a general feature of the scattering theory. A deviation of a phenomenological scattering amplitude from the natural one is interpreted by an effective pole term interaction of genuine nature which can not be described by the mesonbaryon dynamics, reminiscent of the CDD pole. Applying the present method to physical mesonbaryon scatterings, we find that the Λ(1405) resonance is dominated by a mesonbaryon component forming a KNπΣ molecularlike structure, while the N(1535) resonance requires some pole contribution.
The research activities at HIRFL cover the fields of radio-biology, material science, atomic physics, and nuclear physics. This report mainly concentrates on the experiments of nuclear physics with the existing and planned experimental setups such as SHANS, RIBLL1, ETF, CSRe and PISA at HIRFL.
We have performed a dynamical calculation of the bound state problem of D0Ｄ*0 by considering the pion and sigma meson exchange potential. Our preliminary analysis disfavors the molecular interpretation of X(3872) if we use the experimental D*Dπ coupling constant g=0.59 and a reasonable cutoff around 1 GeV, which is the typical hadronic scale. In contrast, there probably exists a loosely bound Swave BB* molecular state. Such a molecular state would be rather stable since its dominant decay mode is the radiative decay through B*→Bγ.
The international HypHI collaboration proposes to perform hypernuclear spectroscopy with stable heavy ion beams and rare isotope beams at GSI and FAIR in order to study neutron and proton rich hypernuclei and to measure directly hypernuclear magnetic moments for the first time. The project is divided into four phases. In the first Phase 0 experiment, the feasibility of precise hypernuclear spectroscopy with heavy ion beams will be demonstrated by observing π- decay channels of 3ΛH, 4ΛH and 5ΛHe with 6Li projectiles at 2 AGeV impinging on a 12C target. In the later Phases 1 through 3, studies of proton and neutron rich hypernuclei, direct measurements of hypernuclear magnetic moments and the spectroscopy of hypernuclei toward the nucleon driplines are planned.
Hypernuclear physics has become very exciting owing to new epochmaking experimental data. Recent progress in theoretical and
experimental studies of hypernuclei and future developments in this field are discussed.
In this proceeding, we will first outline the experimental setup and main results of the most recent hypernuclear γray spectroscopy experiment (KEKE566) performed at KEKPS K6 beam line. The main feature and characteristics of this type of research will be emphasised. After that, the approved experimental proposal (E13) at JPARC facility will be introduced briefly.
We have studied Z+(4430)as a D*D1 molecule from the quark model, state mixing effect is considered by solving the coupled channel Schrdinger equation numerically. More precise measurements of Z+(4430)mass and width, partial wave analysis are helpful to understand its structure. If it lies below the D*D1 threshold, molecule interpretation with JP=1- is favored, and JP=0- can not be ruled out. Otherwise Z+(4430)may be a virtual state with JP=2-. The analogous heavy flavor mesons Z+bb and Z++bc are considered as well, and the masses predicted in our model are in agreement with the predictions from the potential model and QCD sum rule.
Thick target yields of α particles emitted in the 6Li(d, α)4He and 7Li(p, α)4He reactions were measured for Li target in the solid and liquid phase. Observed reaction rates for the liquid Li are always larger than those for the solid. This suggests that the stopping power of hydrogen ion in the liquid Li metal might be smaller than in the solid. Using the empirically obtained stopping power for the liquid Li, we have deduced the screening potentials of the Li+p and Li+d reactions in both phases. The deduced screening potential for the liquid Li is about 500 eV larger than for the solid. This difference is attributed to the effect of liquefied Li+ ions. It is concluded that the ionic screening is much stronger than the electronic screening in a lowtemperature dense plasmas.
Some special issues of the random phase approximation(RPA) in the relativistic approach are reviewed. A full consistency and proper treatment of coupling to the continuum are responsible for the successful application of the RPA in the description of dynamical properties of finite nuclei. The fully consistent relativistic RPA(RRPA) requires that the relativistic mean filed (RMF) wave function of the nucleus and the RRPA correlations are calculated in a same effective Lagrangian and the consistent treatment of the Dirac sea of negative energy states. The proper treatment of the single particle continuum with scattering asymptotic conditions in the RMF and RRPA is discussed. The full continuum spectrum can be described by the single particle Green’s function and the relativistic continuum RPA is established. A separable form of the paring force is introduced in the relativistic quasiparticle RPA.
By using a simple barrier penetration approach, we predict the αdecay branching ratios to members of groundstate rotational band of heavy eveneven No isotopes. We also extend our approach to calculate the αdecay branching ratios to the rotational band of heavy oddA nuclei. The theoretical branching ratios of αdecays are found in good agreement with the available experimental data.
We investigate a Σmixing probability of a neutronrich Λhypernucleus 10ΛLi by using microscopic shellmodel calculations considering a ΛΣ coupling in the first order perturbation. The theoretical Σmixing probability in 10ΛLi is found to be about 0.48%,
due to the appearance of multiconfiguration Σ Nuclear excited states which can be strongly coupled with the Λ ground state in 10ΛLi.
The level structures of neutronrich 105Mo, 106Mo, 108Mo and 110Ru nuclei in A ≈ 100 region have been carefully investigated by coincidence measurements of the prompt γrays populated in the spontaneous fission of 252Cf with the Gammasphere detector array. In 105Mo, onephonon K=9/2 and twophonon K=13/2 γvibrational bands have been identified. In 108Mo, onephonon γvibrational band is expanded and twophonon γvibrational band has been identified. Two similar sets of bands in 106Mo and 110Ru are observed to high spins, which have been proposed as the soft chiral γvibrational bands. The characteristics for these γvibrational bands and chiral doublet bands have been discussed.
The lifetime of the first excited 2+ state in 18C was measured using an upgraded recoil shadow method to determine the electric quadrupole transition. The measured mean lifetime is 18.9 ±0.9(stat)±4.4(syst)ps, which corresponds to a B(E2; 2+1→0+gs) value of (4.3± 0.2 ±1.0) e2fm4, or about 1.5 Weisskopf units. The mean lifetime of the first 2+ state in 16C was remeasured to be about 18 ps, about four times shorter than the value reported previously. This discrepancy was explained by incorporating the γray angular distribution measured in this work into the previous measurement. The observed transition strengths in 16,18C are hindered compared to the empirical transition strengths, indicating that the anomalous hindrance observed in 16C persists in 18C.
We develop a new framework for the study of the nuclear matter based on the linear sigma model. We introduce a completely
new viewpoint on the treatment of the nuclear matter with the inclusion of the pion. We extend the relativistic chiral mean field
model by using the similar method in the tensor optimized shell model. We also regulate the pionnucleon interaction by considering
the formfactor and short range repulsion effects. We obtain the equation of state of nuclear matter and study the importance
of the pion effect.
We are carrying out hadron photoproduction experiments by using polarized photon beams at SPring8 in Japan. In 2005, we
started developing a polarized HD target for future experiments using both the polarized photon beams and the polarized target. The
polarized HD target is an idealistic target for experiments observing reactions with small cross sections because the HD does
not include heavy nuclei which produce many background events. The measurement of double polarization asymmetries is expected to give much important information to investigate the nucleon hidden structure, hadron photoproduction dynamics, and exotic hadron property. We report on the present status of the development of the polarized HD target at RCNP.
The reactions γd→π-pp and γd→npπ+π- have been studied in an energy range from 0.8 to 1.1 GeV at the tagged photon facility of Laboratory of Nuclear Science, Tohoku University. Charged pions and protons in the final state were measured by using the Neutral Kaon Spectrometer (NKS2). The analysis of the γd→π-pp was mainly used to check the acceptance of the NKS2 and to calibrate the tagged photon energy. The photoproduction of the Δ++Δ- was identified in the γd→npπ+π- reaction. Since the data analyses are still in progress, we issue an interim report and preliminary results.
We are now preparing for the third generation (e, e′ K+) Λ hypernuclear spectroscopic experiment at Hall C, Jefferson Lab (USA). The goal of the experiment is the precise spectroscopy of hypernuclei in wide mass region. We have constructed a new high resolution electron spectrometer “HES” dedicated to (e, e′ K+) hypernuclear study in Japan and it was shipped to JLab in February, 2008. We will discuss about the physics of the (e, e′ K+) hypernuclear study at JLab and report the current preparation status of the third generatrion experiment.
Recently we have constructed two facilities for generating photon beams in the MeV and subMeV energy regions by means of the
Compton backscattering with a laser and an electron beam at SPring8 and at Kansai Photon Science Institute of Japan Atomic Energy Agency(KPSIJAEA). The MeVphoton source at SPring8 consists of a continuouswave opticallypumped far infrared laser with a wavelength of 118.8 μm and an 8 GeV stored electron beam. Present MeVphoton flux is estimated to be 1.3×103
photons/s. On the other hand, the subMeVphoton source at KPSIJAEA consists of a pulse Nd∶YAG laser with a wavelength of
1 064 nm and a 150 MeV electron beam accelerated by microtron. In the first trial of the photon production in this source, backscattered photon flux is estimated to be 20 photons/pulse. Both the Compton backscattered photon sources have possibilities to be used for new tools in various fields such as nuclear physics, materials science, and astronomy.
We investigate the properties of the ηnucleus interaction by postulating the N*(1535) dominance for ηN system. Since the mass gap of N* and N is very close to the η meson mass, there is the possibility of the level crossing between the N*h and η modes in finite density. We postulate the N*(1535) resonance for the ηN system and consider quite distinct N* properties in finite density which are predicted by two independent chiral models. We find that we can obtain clearer information on the inmedium N* properties and also on the ηnucleus interaction through the formation of the ηmesic nuclei by (π, N) reactions under the appropriate experimental conditions, which can be performed at existing and/or forthcoming facilities like JPARC.
Differential and total cross sections of the γp→π0p and the γd→π0pn reaction were measured for photon energies between 640 and 1 150 MeV. The data have been compared with SAID and MAID model calculations. π0 photoproduction on the deuteron shows a strong suppression of the 2nd resonance which is clearly seen in the γp→π0p reaction.
Laser Compton scattering(LCS) can generate Xrays or γrays with high brightness and easy controlled polarization by applying highpeakpower laser pulses to relativistic electron bunches. One of the most promising approaches to short pulsed Xray sources is the laser synchrotron source. It is based on LCS between picoseconds relativistic electron bunches and picoseconds laser pulses. A project of Shanghai laser electron gamma source with LCS method has been proposed on Shanghai synchrotron radiation facility. Before that, a prototype has been developed in the beamline of the linear accelerator at the Shanghai Institute of Applied Physics, Chinese Academy of Sciences. The LCS experiment was carried out by using the 107 MeV, 5 Hz, 1 ns, 0.1 nC electron bunches from the linear accelerator and the 18 ns, 10 MW peak power, Nd∶YAG laser pulses. In this communication, we describe the details and report the first results of this experiment.
A simple Xray spectrometer and a PCBased Data Acquisition System(DAS) have been developed newly in Shanghai Institute of Applied Physics(SINAP), Chinese Academy of Sciences(CAS) for the measurement of the Xray source generated using laser Compton scattering. The system consists of liquid nitrogen cooled high resolution Si(Li) detector, electronics and a DAQ. The Si(Li) detector was designed and made by Center of Advanced Instruments in SINAP, CAS， it allows us to measure Xrays with the energy up to 60 keV and the energy resolution(FWHM) of 184 eV at 5.9 keV. We measured the system uncertainty was 0.2 eV and time drifting of detector was 0.05% both at 5.9 keV. The DAQ was based on ObjectOriented software LabVIEW 7.1, it has data online analysis and original data saved functions.
We would like to emphasize that the inflight (K-, N) reactions are particularly useful for the study of the Knucleus interaction. Since the reaction mechanism is well known, there is little ambiguity to derive the Knucleus interaction from the measured missing mass spectra. Here we discuss the missing mass spectra of the (K-, N) reactions on the 12C and 16O targets. The spectra show an appreciable amount of strength below the Knucleus threshold which indicates that the Knuclear potential is strongly attractive. Comparison of the missing mass spectra with theoretical calculations leads to a potential depth of around -190 MeV for the 12C(K-, n) reaction. A less deep potential of around -160 MeV reproduces well that of the 12C(K-, p) reaction. The difference can be due to isospin dependence of the interaction. Our data show that the Knucleus potential is very deep to realize kaon condensation in the core of neutron stars.
Spin structure is one of the fundamental subjects in the study of nucleon structure. Recently it is found that Generalized Parton Distributions(GPDs) are related to the total angular momentum carried by partons, which offers a possible solution to the spin puzzle in the first time. We get access to certain GPDs by looking at the azimuthal angle asymmetries attributed to the interference between Deeply Virtual Compton Scattering(DVCS) and BetheHeilter processes in HERMES experiment. By measuring the asymmetry with respect to transverse target polarization from proton target, a modeldependent constraint on Ju vs Jd is obtained. Another worldwide unique channel is nuclear DVCS. The preliminary results on asymmetries with respect to beam spin and beam charge are
We study the states π1(1600) and π1(2015) in the QCD sum rule. We classify the tetraquark currents of the quantum numbers IGJPC=1-1-+, and find that the flavor structure (3 6 )(6 3 ) is preferred when using a diquarkantidiquark construction. By using both the SVZ and finite energy sum rules, we obtain a mass around 1.6 and 2.0 GeV, for the states with the quark contents qq and qs , respectively. We also study their decay patterns.
We study kaon photoproduction from the nucleon. Using the photon beam asymmetry, we discuss the couplings of the K and K* mesons with baryons. In previous studies of photoproductions, the K* coupling strength has been treated as parameters to reproduce experimental data. Here instead we propose to use the coupling strength which is derived from a microscopic escription. By including a higher order loop contribution induced by the QCD anomaly, we demonstrate that the experimental data can be explained well. The use of a microscopic description enables us a better understanding of the reaction dynamics which provides further basis of hadron dynamics.
The NΔ and ΔΔ dibaryon resonances are studied by calculating the NN scattering phase shifts with explicitly coupling these dibaryon channels in a multichannel coupling calculation with two quark models. These quark models, the chiral quark model and quark delocalization color screening model, describe the NN S, Dwave phase shifts below the π production threshold quantitatively well. Both quark models predict the 1D2 resonance discovered in NN partial wave phase shift analysis and the J=1 or 3 isoscalar resonance recently reported by CELSIUSWASA Collaboration are NΔ5S2 and ΔΔ7S3 resonance, respectively. Further measurements at COSY, LEPS and Lanzhou Cooling Storage Ring(CSR) to check the ΔΔ resonance are discussed.
We present meson production in Cu+Cu and Au+Au collisions measured by the STAR experiment at RHIC.The hadronic decay mode → K+K-is used in the analysis.The yields for meson in Cu+Cu and Au+Au collisions at a given beam energy are scaled by the number of participant.The Npart normalized meson yields in heavy ion collisions over those from p+p collisions are larger than 1 and increase with collision energy.These results suggest that the source of enhancement of strange hadrons is related to the formation of a dense medium in high energy heavy ion collisions and can not be only due to canonical suppression of their production in smaller systems.We also present STAR results on the meson elliptic flow v2 from sNN=200 GeV Cu+Cu at RHIC.The elliptic flow in Cu+Cu system that has the similar relative magnitude and qualitative features as that in Au+Au system.The observations imply the hot and dense matter with partonic collectivity has been formed in heavy ion collisions at RHIC. However, eccentrality normalized v2, v2/(nqεpart) is lower for Cu+Cu than for Au+Au collisions at 200 GeV.So this might indicate thermalization has not been reached in 200 GeV Cu+Cu collisions.
We study the Σ*Δ interaction in the chiral SU(3) quark model and in the extended chiral SU(3) quark model. In these two models, the shortrange interaction mechanism are totally different, one is from the onegluon exchange and another is from the vector meson exchange. The possible reasons of forming strangeness -1 bound states are given. Comparisons between the cases with and without quark exchange effect are made. The results show the quark exchange effect does give attractions to (Σ*Δ)ST=0 52 and (Σ*Δ)ST=3 12 systems, which means the special symmetry is important. Also, we make some analysis on chiral field effect, our results show that the σ exchange dominantly provides the attractive interaction for these two states.
Proton resonant states in 22Mg have been investigated by the resonant elastic scattering of 21Na+p. The 21Na beam with a mean energy of 4.00 MeV/u was separated by the CNS radioactive ion beam separator(CRIB) and bombarded a thick(CH2)n target. The energy spectra of recoiled protons were measured at scattering angles of θcm ≈172° and 146°, respectively. A new state at 7.06 MeV has been observed clearly and another new one at 7.28 MeV is tentatively identified due to its low statistics. The roton resonant parameters were deduced from an Rmatrix analysis of the differential cross section data. The astrophysical esonant reaction rate for the 18Ne(α, p)21Na reaction has been estimated, and it is about five times larger than that assumed before.
Signature inversion in oddodd nuclei is investigated by using a proton and a neutron coupling to the coherent state of the core. Two parameters are employed in the Hamiltonian to set the energy scales of rotation, neutronproton coupling and their competition. Typical level staggering is extracted from the calculated level energies. The calculation can approximately reproduce experimental signature inversion. Signature inversion is attributed to the rotational motion and neutronproton residual interaction having reversed signature splitting rules. It is found signature inversion can appear at axially symmetric shape and highK band.
We recently performed a series of improvement on evaluation of eigenvalues without complicated iterations. In this work we first discuss evaluation of the lowest eigenvalue for given systems, by which one conveniently obtains the value of the lowest eigenvalue based on the dimension and width of given matrix. We also discuss a strong correlation between eigenvalues and diagonal matrix elements for large matrices, by which one is able to predict eigenvalues approximately without iterations.
Within the concept of the dinuclear system(DNS), by incorporating the coupling of the relative motion to the nucleon transfer process, a dynamical model is proposed for describing the formation of superheavy residue nucleus in massive fusion reactions, in which the capture of two heavy colliding nuclei, the formation of compound nucleus and the deexcitation process are calculated using empirical coupled channel model, solving master equation numerically and statistical theory, respectively. By using the DNS model, the evaporationresidue excitation functions in the 48Ca induced fusion reactions and in the cold fusion reactions are investigated systematically and compared with available experimental data. Optimal evaporation channels and combinations as well as the corresponding excitation energies are proposed. The possible factors that influencing the isotopic dependence of the production cross sections are analyzed. The formation of the superheavy nuclei based on the isotopes U with different projectiles are also investigated.
The ground state properties of Hs nuclei studied in the framework of the relativistic mean field theory revealed that more stable isotopes are located on the proton abundant side of the chain. The last stable nucleus to the proton drip line is 256Hs. The most stable unknown Hs nucleus may be 268Hs. The density dependent delta interaction pairing is used to improve the BCS pairing correction, which results in more reasonable singleparticle energy level distributions and nucleon occupation, and it is shown to be available to describe the properties of nuclei in the superheavy region.
The relationship between the centroid energies of the isovector giant dipole resonance of finite nuclei and the symmetry energy has been studied. It is found the excitation energies of the dipole resonance in finite nuclei are correlated linearly with the symmetry energy at and below the saturation density. This linear correlation leads to the symmetry energy at the saturation density at the interval 33.0 MeV ≤ S(ρ0) ≤ 37.0 MeV, and the symmetry energy at ρ = 0.1 fm-3 at the interval 21.2 —22.5 MeV. It is proposed that a precise measurement of the dipole mode in nuclei could set up an important constraint on the equation of state for nuclear matter.
With the commissioning of the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou (HIRFLCSR), a pilot experiment operating the CSRe in isochronous mode to test the power of HIRFLCSR for measuring the mass of the shortlived nucleus was performed in December of 2007. The fragments with A/q = 2 of 36Ar were injected into CSRe and their revolution frequencies were measured with a fast time pickup detector with a thin foil in the circulating path of the ions. The preliminary result is presented. The result shows the potential of CSRe for mass measurements of shortlived nuclei.
A diquark model is used to investigate singlecharmed baryons. In this model, baryon is composed of two diquarks and an antiquark. Masses of lowest lying states with JP=1/2± are obtained. Baryons in our results are as heavy as other theoretic predictions and we suggest that the fivequark components should be considered in any threequark model for studying the charmed baryons.