ANisotropic Flow in high baryon density region

We report a systematic study of the first two Fourier coefficients v1 and v2 in the center of mass energy range 2.11-4.9 GeV within the framework of a hadronic transport model (UrQMD). Recent results from the STAR experiment were used to test the model calculations. A mean-field mode with strong repulsive interaction is needed to reproduce the 10-40% centrality data at 3 GeV. This implies that hadronic interactions play an important role in the collective flow development in the high baryon density region. The mean values of the freeze-out time for protons and pions are shifted earlier owing to the additional repulsive interactions. We predict the energy dependence of the mean values of transverse momentum, v1, and v2 for both protons and pions from the Au+Au collisions.

本研究基于强子输运模型（UrQMD），针对质心系能量区间2.11~4.9 GeV内的前两阶傅里叶系数v1与v2开展系统性研究。采用STAR实验的最新结果对模型计算结果进行验证。在3 GeV能区，需引入具备强排斥相互作用的平均场模式，方可复现10%~40%中心度的实验数据。该结果表明，在高重子数密度区域，强子相互作用对集体流的演化具有关键作用。受额外排斥相互作用影响，质子与π介子的冻出时间平均值均有所提前。本研究还预言了金-金（Au+Au）碰撞中质子与π介子的横向动量、v1及v2平均值的能量依赖特性。