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arXiv 2003.04734hep-phnucl-th
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重离子碰撞中物质的等熵演化及临界终点的寻找

Isentropic evolution of the matter in heavy-ion collisions and the search for the critical endpoint

Mario Motta, Rainer Stiele, Wanda Maria Alberico, Andrea Beraudo

摘要:

我们研究了在相对论性重离子碰撞中产生的物质的等熵演化,对于正在进行的和未来的QCD相图中的临界端点(CEP)的实验搜索的感兴趣的每重子熵比的各种值:这些包括目前的束能量扫描(BES)计划在RHIC和固定目标碰撞预计在不久的将来在各种设施。我们用两种不同的有效拉格朗日量:PNJL(Polyakov-Nambu-Jona-Lasinio)和PQM(Polyakov-quark-meson)模型来描述热密物质。我们专注于量预期有一个直接的实验相关性:声速,负责集体加速度的火球,和广义磁化率,连接到累积量的保守电荷的分布。原则上,它们应该影响动量谱和已识别粒子产额的逐事件波动。以实际的初始温度和熵每重子比的值,我们研究的时间演化的上述数量的差异沿等熵轨迹覆盖QCD相图的不同区域,通过远离或接近CEP,甚至相交的一阶临界线。

英文摘要:

We study the isentropic evolution of the matter produced in relativistic heavy-ion collisions for various values of the entropy-per-baryon ratio of interest for the ongoing and future experimental searches for the critical endpoint (CEP) in the QCD phase diagram: these includes the current Beam-Energy-Scan (BES) program at RHIC and the fixed-target collisions foreseen for the near future at various facilities. We describe the hot-dense matter through two different effective Lagrangians: the PNJL (Polyakov-Nambu-Jona-Lasinio) and the PQM (Polyakov-quark-meson) models. We focus on quantities expected to have a direct experimental relevance: the speed of sound, responsible for the collective acceleration of the fireball, and the generalized susceptibilities, connected to the cumulants of the distributions of conserved charges. In principle, they should affect the momentum spectra and the event-by-event fluctuations of the yields of identified particles. Taking realistic values for the initial temperature and the entropy-per-baryon ratio we study the temporal evolution of the above quantities looking for differences along isentropic trajectories covering different regions of the QCD phase diagram, passing far or close to the CEP or even intersecting the first-order critical line.

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