Article title: Anisotropic flow in high baryon density region

高重子密度区域的各向异性流

DOI:10.1007/s41365-022-01006-0

One sentence summary:

一句话概要：

Hadronic interactions play a significant role in developing collective flow in the high-baryon-density region.

强子相互作用在高重子密度区域集体流的发展中起着重要作用。

http://www.nst.sinap.ac.cn/newsDetails/112/26553/en/

The Novelty (What)

创新性（主要内容）

This study showed the significance of hadronic interactions in developing collective flow in the high-baryon-density region. The statement was derived from the finding whereby a mean-field mode with strong repulsive interaction is needed to reproduce the recent STAR results of 10–40% centrality at √s_NN = 3 GeV. Besides that, the energy dependence of directed and elliptic flows was discussed comprehensively. The research was conducted based on Monte Carlo event samples of Au+Au collisions at center of mass energies of √ sNN = 2.11 – 4.9 GeV generated by version 3.4 of the UrQMD model (including both cascade and mean-field modes). These findings contribute to a richer knowledge base in particle physics.

这项研究揭示了强子相互作用在高重子密度区域集体流发展中的意义。 这一结论是由一个具有强排斥相互作用的平均场模式的发现推导出来的，该模式需要重现在STAR质心能量为√s_NN = 3 GeV的近期10-40%中心度的结果。 此外，还对有向流和椭圆流的能量依赖关系进行了全面的讨论。 研究基于URQMD模型3.4版本（包括级联模式和平均场模式）产生的质心能√ sNN = 2.11 – 4.9 GeV的Au+Au碰撞Monte Carlo事件样本。 这些发现有助于在粒子物理学中建立更丰富的知识基础。

The Background (Why)

研究背景（主要原因）

High-energy (relativistic) heavy-ion collisions produce an enormous amount of subatomic particles in all directions. In such collisions, the term “flow” describes how energy, momentum, and number of these particles vary with direction. Collective flow describes a movement of a large number of subatomic particles either in a common direction or at a common magnitude of velocities. Meanwhile, elliptic flow measures how the flow is not uniform in all directions when viewed along the beamline. Besides proving the existence of quark-gluon plasma, elliptic flow is one of the most important observations measured at the Relativistic Heavy Ion Collider (RHIC). A recent study conducted by Solenoidal Tracker at RHIC (STAR) implied that the hadronic interactions dominated the equation of state in collisions at center of mass energies of √ sNN = 3 GeV (a region with baryon chemical potential of 750 MeV). As an effort to explore phase structure in the high baryon density region, this research deployed a hadronic transport model, known as the ultra-relativistic quantum molecular dynamics model (UrQMD), to study the directed and elliptic flows in the high baryon density region by using Monte Carlo event samples of Au+Au collisions. Other than marking a new milestone for the second phase of the beam energy scan at the RHIC (BES-II) program, the outcome paves the path to understanding experimental data from upcoming experimental facilities focused on the high baryon density region.

高能（相对论性）重离子碰撞在各个方向产生大量的亚原子粒子。 在这种碰撞中，“流”一词描述了这些粒子的能量、动量和数量如何随方向而变化。 集体流描述了大量亚原子粒子沿共同的方向或以共同的速度大小运动。 同时，椭圆流测量了当沿束线观察时，流动在各个方向上是如何不均匀的。 椭圆流是相对论重离子对撞机(RHIC)观测到的最重要的现象之一，它不仅证明了夸克胶子等离子体的存在。 RHIC(STAR)的螺线管跟踪器最近进行的一项研究表明，在质心能量√ sNN = 3 GeV（重子化学势为750 MeV的高重子密度区域）的碰撞中，强子相互作用主导了状态方程。 为了探索高重子密度区的相结构，本研究采用强子输运模型，即超相对论量子分子动力学模型(URQMD)，利用Au+Au碰撞的蒙特卡罗事件样本，研究了高重子密度区的定向流和椭圆流。 除了标志着RHIC（BES-II）计划第二阶段束流能量扫描的一个新里程碑之外，这一结果为理解即将到来的聚焦于高重子密度区域的实验设施的实验数据铺平了道路。

The SDG impact (Big Why)

SDG影响力（研究意义）

A better understanding of the properties of the high baryon density region is essential in facilitating future research related to particle physics. This is crucial as the advancement of particle physics will directly impact the expansion of nuclear physics and other closely connected fields. In extension, such enhancement of advanced physics research contributes to the realization of 9^th UNSDG: Industry, Innovation & Infrastructure.

更好地理解高重子密度区域的性质对于促进未来与粒子物理有关的研究至关重要。 这是至关重要的，因为粒子物理的进步将直接影响核物理和其他密切相关领域的扩展。 从广义上说，加强高等物理研究有助于实现联合国可持续发展目标第九条：工业、创新和基础设施。