相对论重离子碰撞中π介子椭圆流劈裂

Elliptic flow splitting of charged pions in relativistic heavy-ion collisions

近年来,美国布鲁克海文国家实验室的相对论重离子对撞机上正在进行着束流能量扫描实验,STAR国际合作组的研究人员发现π介子椭圆流劈裂与电荷不对称度存在着线性关系.该现象被认为是手征磁波效应的重要信号.本文基于拓展的多相输运模型,利用三味Nambu-Jona-Lasinio(NJL)模型研究了构成π+和π-介子不同的夸克同位旋平均场势,为解释π介子椭圆流劈裂与电荷不对称度线性关系的实验现象提供了新思路,可为同质异素体碰撞以及致密星体中夸克物质同位旋效应研究提供理论依据.

Relativistic heavy-ion collisions are an important experimental way of studying the new state of matter as well as the phase diagram of the quantum chromodynamics(QCD)under extremely high temperatures and high densities.In recent years,the beam-energy scan program has been carried out on the relativistic heavy-ion collider at Brookhaven National Laboratory in USA,and the STAR collaboration at relativistic heavy ion v2π-π+collision(RHIC)has measured the difference in the elliptic flow between and on an event-by-event basis,and found a linear dependence on the charge asymmetry Ach of the collision system,which is considered as a possible signal of the chiral magnetic wave.Based on the extended multi-phase transport model(AMPT),this paper uses a 3 flavor Nambu-Jona-Lasinio(NJL)model to study the quark isospin Mean-field potential,which provides a new idea for explaining the experimental phenomenon of the linear relationship between the∆v2=v2(π-)-v2(π+)pion elliptic flow splitting and charge asymmetry Ach.Our results show that isovector interaction can cause a splitting of the isospin asymmetric quark matter mean-field potential,manifesting as d(¯u)u(¯d)d(¯u)quarks experiencing a mean-field potential greater than quarks.Therefore,quarks experience u(¯d)more repulsion than quarks in collision processes,resulting in a small increase in the elliptic flow of the v2(d)v2(¯u)v2(u)v2(¯d)πpartial subflow and,while and decrease slightly.In the hadronization process,the d u¯u¯delliptic flow splitting occurs due to the split of and elliptic flows combined with the split of and elliptic flows.We also found a linear correlation between charge asymmetry and isospin asymmetry at mid-rapidity region from our transport model,and thus explained the experimental phenomenon of the linear∆v2relationship between the pion elliptic flow splitting and charge asymmetry Ach by using the isospin mean-field potential of quark matter.Further,isospin properties of quark matter also provide a theoretical basis for isobar collisions and the equation of state of compact star matter.