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岳晓清, 李鹏程, 王永佳, 李庆峰, 刘福虎. 质心能量7.7 GeV下Au+Au碰撞中初始密度涨落对累积矩的影响[J]. 原子核物理评论, 2024, 41(1): 551-557. DOI: 10.11804/NuclPhysRev.41.2023CNPC25
引用本文: 岳晓清, 李鹏程, 王永佳, 李庆峰, 刘福虎. 质心能量7.7 GeV下Au+Au碰撞中初始密度涨落对累积矩的影响[J]. 原子核物理评论, 2024, 41(1): 551-557. DOI: 10.11804/NuclPhysRev.41.2023CNPC25
Xiaoqing YUE, Pengcheng LI, Yongjia WANG, Qingfeng LI, Fuhu LIU. Effects of Initial Density Fluctuations on Cumulants in Au+Au Collisions at 7.7 GeV Center-of-Mass Energy[J]. Nuclear Physics Review, 2024, 41(1): 551-557. DOI: 10.11804/NuclPhysRev.41.2023CNPC25
Citation: Xiaoqing YUE, Pengcheng LI, Yongjia WANG, Qingfeng LI, Fuhu LIU. Effects of Initial Density Fluctuations on Cumulants in Au+Au Collisions at 7.7 GeV Center-of-Mass Energy[J]. Nuclear Physics Review, 2024, 41(1): 551-557. DOI: 10.11804/NuclPhysRev.41.2023CNPC25

质心能量7.7 GeV下Au+Au碰撞中初始密度涨落对累积矩的影响

Effects of Initial Density Fluctuations on Cumulants in Au+Au Collisions at 7.7 GeV Center-of-Mass Energy

  • 摘要: 重离子碰撞中的密度涨落效应及其对观测量的影响是核物理研究领域的一个重要方向。本文利用极端相对论量子分子动力学(UrQMD)模型,通过改变初始化时两个核子之间的最小距离d_\min^,讨论了碰撞能量\sqrts_\rmNN^= 7.7 GeV下Au+Au碰撞中初始密度涨落对净质子多重数分布累积矩的影响。结果发现,当d_\min^从1.6 fm减小到1.0 fm时,坐标空间中初态密度涨落增大。在火球膨胀阶段,d_\min^引起的初始密度涨落效应对累积矩的影响逐渐减弱,平均场的效应逐渐显著。在末态的动量空间中,较小的赝快度窗口(\varDelta \eta \leqslant 4)下初态密度涨落对净质子数分布涨落的影响较小;然而在一个较大的赝快度窗口下(\varDelta \eta > 4),其对净质子数的累积矩比值有着较为明显的影响,在半中心碰撞(b= 5 fm)中,d_\min^所带来的的影响大约为平均场所带来影响的2~3倍。

     

    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 \sqrts_\rmNN^= 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.

     

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