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

作　　者：岳晓清 李鹏程 王永佳[2] 李庆峰[2,3] 刘福虎[1] YUE Xiaoqing;LI Pengcheng;WANG Yongjia;LI Qingfeng;LIU Fuhu(Institute of Theoretical Physics,Shanxi University,Taiyuan 030006,China;School of Science,Huzhou University,Huzhou 313000,Zhejiang,China;Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou 730000,China)

机构地区：[1]山西大学理论物理研究所,太原030006 [2]湖州师范学院理学院,浙江湖州313000 [3]中国科学院近代物理研究所,兰州730000

出　　处：《原子核物理评论》2024年第1期551-557,共7页Nuclear Physics Review

基　　金：国家自然科学基金资助项目(12335008,U2032145);国家重点研发计划资助项目(2020YFE0202002);山西省自然科学基金(202103021224036)。

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/S_(NN)=7.7GeV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1.6fm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(Δ_(η)≤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(Δ_(η)>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。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 /S_(NN)=7.7GeV 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 pseudorapidity window(4n≤4)is negligible.However,in a broad pseudo-rapidity window(4n>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.

关 键 词：重离子碰撞 初始密度涨落 输运模型 累积矩 

分 类 号：O571.6[理学—粒子物理与原子核物理]