Au+Au重离子碰撞中5~200 GeV碰撞能量下的温度涨落与比热(英文)

使用多相输运（AMPT）模型来研究相对论重离子碰撞中强子物质的比热（C_V）与对撞能量的关系以及温度的高阶涨落，并将之与文献PhysRevC.94.044901]实验数据的比热结果进行了比较。对经历相变的系统，比热（C_V）作为表征系统状态方程的热力学量，其值预期在临界点发散。而温度的高阶涨落对相变敏感，比热（CV）和温度的高阶涨落都是适于探测QCD相变和临界点的敏感探针。通过逐个事例的平均横动量（<p_T>）来提取有效温度T_eff，再通过粒子的有效温度T_eff的分布提取出了相应粒子的热容。通过有效温度（T_eff）的分布的高阶矩来计算温度的高阶涨落。发现AMPT模型中比热和温度的高阶矩都随温度单调递减。同时还发现在低碰撞能量时，实验数据的比热结果有随能量增加而有一个急速下降，与AMPT模型的走势显著不同。AMPT模型中没有QCD临界点，提供了一个无临界点的参考背景。AMPT模型的计算结果可与实验结果比较作为实验上寻找QCD临界点的参考。

Temperature Fluctuation and the Specific Heat in Au+Au Collisions at Collision Energies from 5 to 200 GeV

We report the results of the energy dependence of specific heat (C_V) of hadronic matter in a multiphase transport (AMPT) model and compared with the experimental results from Ref.PhysRevC.94.044901]. The temperature high order fluctuations in Au+Au collisions in AMPT model are also reported. C_V is a thermodynamic quantity that characterizes the equation of state of the system. For a system undergoing phase transition, C_V is expected to diverge at the critical point. Fluctuations of temperature are sensitive observables to probe the QCD critical point. The C_V is extracted by analyzing the data on event-by-event mean transverse momentum (<p_T>). The <p_T> distributions in finite p_T ranges are converted to distributions of effective temperature (Teff). The C_V is extracted from the T_eff distributions. The fluctuations of temperature are measured by calculating the high order cumulants of the T_eff distributions. We find that both C_V and high order cumulants of the temperature show monotonic distributions in energy dependence, which is expected that there is no phase transition critical point in the AMPT model. At low energies, a sharp drop of C_V from the experimetal results is observed and it deviates from the AMPT results. The AMPT model can provide a non-critical background, which can provides a good reference for comparison with experimental results to search for the QCD critical point.