论文标题
重离子碰撞在中间能量上的椭圆流：冲击参数，平均场电位和碰撞项的作用
Elliptic flow in heavy-ion collisions at intermediate energy: the role of impact parameter, mean field potential, and collision term
论文作者
论文摘要
在超级量子分子动力学（URQMD）模型中，在整个反应过程中最终以中高度（| $ y_0 $ | <0.1）发出的核子，这些椭圆流的时间演变（$ v_2 $）在这些collions in au+au usion use $ 0.4 gev $/clibions of unives use $ $ $/gev的时间演变（$ v_2 $）的时间演变（$ v_2 $）被研究。 $ v_2 $的初始值为正值，并随$ b $增加而增加，然后随着时间的流逝而减小，并且倾向于以负值饱和。发现核素核子碰撞始终降低$ v_2 $的值（增强平面外排放），而核平均场电位在外围反应的扩展阶段可能会稍微提高$ v_2 $的值。发现相关密度大多由$ v_2 $的核子探测到中高度的核子，为$ \ sim $ \ sim $ 60％的$ 60％的碰撞期间最大密度的60％。
Within the ultrarelativistic quantum molecular dynamics (UrQMD) model, by reverse tracing nucleons that are finally emitted at mid-rapidity (|$y_0$| < 0.1) in the entire reaction process, the time evolution of elliptic flow ($v_2$) of these traced nucleons produced in Au+Au collisions at beam energy of 0.4 GeV$/$nucleon with different impact parameters ($b$) is studied. The initial value of $v_2$ is positive and increases with $b$, then it decreases as time passes and tends to saturate at a negative value. It is found that nucleon-nucleon collisions always depress the value of $v_2$ (enhance the out-of-plane emission), while the nuclear mean field potential may slightly raise the value of $v_2$ during the expansion stage in peripheral reactions. The related density mostly probed by $v_2$ of nucleons at mid-rapidity is found to be $\sim$ 60% of the maximum density reached during the collisions.
