Quartic cumulant of baryon number in the presence of a QCD critical point
Quartic cumulant of baryon number in the presence of a QCD critical point
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DOI：
10.1103/physrevc.103.034901
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发表时间：
2020-08
影响因子：
3.1
通讯作者：
D. Mroczek;A. N. Acuna;J. Noronha-Hostler;P. Parotto;C. Ratti;M. Stephanov
中科院分区：
文献类型：
--
作者：
D. Mroczek;A. N. Acuna;J. Noronha-Hostler;P. Parotto;C. Ratti;M. Stephanov
在相对论重离子对撞机正在进行的寻找QCD临界点的背景下，我们研究了温度和重子化学势面临界点附近的状态方程。我们使用早期文献中介绍的参数表示，它使用几个非通用参数将通用三维Ising状态方程映射到QCD相图上。我们关注重子数的四次累积量，或重子数磁化率${\ensuremath{\chi}}_{4}^{B}$，它可以通过净质子波动峰度测量得到。最初，通过基于领先奇异贡献的普适性论证，预测${\ensuremath{\chi}}_{4}^{B}$和净质子峰度由于临界点的存在而表现出特定的非单调性。特别是，当沿着相图上的冻结曲线减小光束能量时，峰度预计会下降，然后在光束能量扫描接近临界点时达到峰值。我们研究了Ising-to-QCD映射的非全称且迄今未知的参数对${\ensuremath{\chi}}_{4}^{B}$行为的影响。我们发现，虽然峰值仍然是一个固体特征，但临界点的存在并不一定导致在转变温度以下的冻结线上${\ensuremath{\chi}}_{4}^{B}$的下降。当子先导奇异项被充分抑制时，临界点对倾角的贡献只出现在一个狭窄的映射参数集上。
In the context of the ongoing search for the QCD critical point at the Relativistic Heavy-Ion Collider, we study the equation of state near the critical point in the temperature and baryon chemical potential plane. We use the parametric representation introduced in earlier literature, which maps the universal three-dimensional Ising equation of state onto the QCD phase diagram using several non-universal parameters. We focus on the quartic cumulant of the baryon number, or baryon number susceptibility ${\ensuremath{\chi}}_{4}^{B}$, which can be accessed experimentally via net-proton fluctuation kurtosis measurements. It was originally predicted, through universality arguments based on the leading singular contribution, that ${\ensuremath{\chi}}_{4}^{B}$ and net-proton kurtosis should show a specific nonmonotonic behavior due to the critical point. In particular, when following the freeze-out curve on the phase diagram by decreasing beam energy, the kurtosis is expected to dip, and then peak, when the beam energy scan passes close to the critical point. We study the effects of the nonuniversal and thus far unknown parameters of the Ising-to-QCD mapping on the behavior of ${\ensuremath{\chi}}_{4}^{B}$. We find that, while the peak remains a solid feature, the presence of the critical point does not necessarily cause a dip in ${\ensuremath{\chi}}_{4}^{B}$ on the freeze-out line below the transition temperature. The critical point contribution to the dip appears only for a narrow set of mapping parameters, when subleading singular terms are sufficiently suppressed.