Effect of the spin-orbit interaction on flows in heavy-ion collisions at intermediate energies
Effect of the spin-orbit interaction on flows in heavy-ion collisions at intermediate energies
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自旋轨道相互作用对中等能量重离子碰撞中流动的影响
DOI：
10.1103/physrevc.90.034606
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发表时间：
2014-08
影响因子：
3.1
通讯作者：
Zhang Feng-Shou
中科院分区：
文献类型：
--
作者：
Guo Chenchen;Wang Yongjia;Li Qingfeng;Zhang Feng-Shou
基于超相对论量子分子动力学 (UrQMD) 模型的更新版本，研究了重离子碰撞中自旋轨道耦合的影响，其中采用了 Skyrme 势能密度泛函。特别是，研究了自旋轨道耦合对 $^{197}$Au+$^{197}$Au 碰撞发射的自由核子定向流和椭圆流的影响，作为束流能量和碰撞参数的函数。我们的结果表明，自旋轨道项对核子流的净贡献可以忽略不计，而自旋向上和自旋向下核子之间的定向流分裂是可见的，特别是在大冲击参数下，并且在束流能量约为 150 MeV$/$核子时发现分裂峰值。我们还发现，自旋向上和自旋向下中子之间的定向流分裂与通过软对称能和刚性对称能计算的中子定向流差异相当，这表明在自旋极化情况下，如果不考虑模型中的自旋自由度，中子定向流不能再用于确定对称能的刚度。
The effect of the spin-orbit coupling in heavy ion collisions is investigated based on an updated version of the ultra-relativistic quantum molecular dynamics (UrQMD) model, in which the Skyrme potential energy density functional is employed. And in special, the spin-orbit coupling effects on the directed and elliptic flows of free nucleons emitted from $^{197}$Au+$^{197}$Au collisions as functions of both the beam energy and the impact parameter are studied. Our results show that the net contribution of the spin-orbit term to flows of nucleons is negligible, whereas a directed flow splitting between spin-up and spin-down nucleons is visible especially at large impact parameters and a peak of the splitting is found at the beam energy around 150 MeV$/$nucleon. We also found that the directed flow splitting between spin-up and spin-down neutrons is comparable with the neutron directed flow difference calculated by a soft and a stiff symmetry energy, indicating that the directed flow of neutrons cannot be used to pin down the stiffness of symmetry energy any more without considering the spin degree of freedom in models in case of spin polarization.