arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2109.07594nucl-thhep-phnucl-ex
收藏

JAM微观模型中的平均场更新:平均场对$\sqrt{s_{NN}}=2-20$ GeV能量的高能重离子碰撞中集体流的影响

Mean-field update in the JAM microscopic model: Mean-field effects on collective flow in high-energy heavy-ion collisions at $\sqrt{s_{NN}}=2-20$ GeV energies

Yasushi Nara, Akira Ohnishi

摘要:

定向流的束流能量依赖性是研究强相互作用物质性质的敏感探针。在相对论量子分子动力学(RQMD)框架下,我们考虑了动量相关强子平均场的不同实现。首先,洛伦兹标量实现的Skyrme型潜在的检查。然后,全面实施的Skyrme型潜在的洛伦兹矢量的RQMD方法的建议。我们发现,标量实施的Skyrme力是太弱,产生排斥解释观测数据的侧向流在$\sqrt{s_{NN}}<10$ GeV,而矢量实施给出了集体流兼容的数据为广泛的光束能量$2.7 <\sqrt{s_{NN}}<20$ GeV。我们表明,我们的方法再现了负质子定向流在$\sqrt{s_{NN}}>10$ GeV的实验发现。讨论了常规强子平均场中定向流的动力学产生机制。在重离子碰撞的压缩阶段,由于高的重子密度而产生的强排斥相互作用,主要产生正斜率的质子定向流。相反,在碰撞的膨胀阶段,由倾斜膨胀和观众物质的遮蔽产生的负向流动比正向流动更强烈。在较低的碰撞能量$\sqrt{s_{NN}}<10$ GeV,正流战胜负流,因为长的压缩时间。另一方面,在更高能量$\sqrt{s_{NN}}>10$ GeV下,由于更短的压缩时间和更长的膨胀时间,负流获胜。从正流到负流的过渡束能量对相互作用的强度高度敏感。

英文摘要:

The beam energy dependence of the directed flow is a sensitive probe for the properties of strongly interacting matter. We consider different implementations of momentum-dependent hadronic mean fields in the relativistic quantum molecular dynamics (RQMD) framework. First, Lorentz scalar implementation of a Skyrme type potential is examined. Then, full implementation of the Skyrme type potential as a Lorentz vector in the RQMD approach is proposed. We find that scalar implementation of the Skyrme force is too weak to generate repulsion explaining observed data of sideward flows at $\sqrt{s_{NN}}<10$ GeV, while vector implementation gives collective flows compatible with the data for a wide range of beam energies $2.7 <\sqrt{s_{NN}}<20$ GeV. We show that our approach reproduces the negative proton directed flow at $\sqrt{s_{NN}}>10$ GeV discovered by experiments. We discuss the dynamical generation mechanisms of the directed flow within a conventional hadronic mean field. A positive slope of proton directed flow is generated predominantly during compression stages of heavy-ion collisions by the strong repulsive interaction due to high baryon densities. In contrast, in the expansion stages of the collision, the negative directed flow is generated more strongly than the positive one by the tilted expansion and shadowing by the spectator matter. At lower collision energies $\sqrt{s_{NN}}<10$ GeV, the positive flow wins against the negative flow because of a long compression time. On the other hand, at higher energies $\sqrt{s_{NN}}>10$ GeV, negative flow wins because of shorter compression time and longer expansion time. A transition beam energy from positive to negative flow is highly sensitive to the strength of the interaction.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑