转动集体流的同位旋效应

在同位旋相关的量子分子动力学模型框架下,通过分析中间快度的方位角分布研究了40MeV/u ⁵⁸Fe+⁵⁸Fe和⁵⁸Ni+⁵⁸Ni反应体系在不同碰撞参数下的转动集体流,并且半经典地计算了转动观测量.发现丰中子体系(⁵⁸Fe+⁵⁸Fe)具有较强的转动集体流,这种现象在半周边碰撞中更加明显.转动集体流的同位旋相关性主要来自于核子–核子碰撞截面的同位旋相关性和对称能的影响.

Isospin Dependence of Rotational Flow

The rotational collective flow in reactions of\ 58 Fe+ 58 Fe and\ 58 Ni+ 58 Ni at 40 MeV/u for different impact parameters was studied within the framework of IQMD model, by analyzing the mid rapidity azimuthal distribution and calculating semi quantitatively the rotational observables. A strong isospin dependence of rotational collective flow has been found, namely, the more neutron rich system exhibits stronger rotational collective flow. This isospin dependence is more appreciable in semi peripheral collisions, and it mainly results from the isospin dependence of N N cross section and the symmetry energy. Meanwhile, it is indicated that the rotational collective flow depends strongly on the impact parameter, namely, it increases with increment of impact parameter from near central to peripheral collisions and then decreases, finally disappears in the most peripheral collisions.