中能重离子碰撞中的碰撞参数研究

Determination of Impact Parameter at Intermediate Energy Heavy Ion Collision

在入射能量Ｅ为４０和１００ＭｅＶ／ｕ时，对^(１１２)Ｓｎ＋^(１１２)Ｓｎ和^(１２４)Ｓｎ＋^(１２４)Ｓｎ两个反应系统在不同碰撞参数下进行了同位旋相关的量子分子动力学模型计算，系统研究了阻塞率、线性动量转移、荷电粒子多重性、轻荷电粒子多重性、中子多重性以及束缚核总电荷Ｚ_(ｂｏｕｎｄ)随碰撞参数的变化规律，结果表明，中子多重性对碰撞参数的依赖在两个能量下都存在着明显的同位旋效应，Ｚ_(ｂｏｕｎｄ)在Ｅ为４０ＭｅＶ／ｕ时存在着同位旋效应．同时讨论了在较低和较高能量时如何更合理地确定反应事件的碰撞参数．

Within the framework of an IQMD model, the stopping rate Erat, linear momen- tum transfer LMT, charged-particle multiplicities N., light charged-particle multiplicities N1c, neutron multiplicities N., and Zbound are investigated as a function of the impact param- eter b in reactions of ~112 Sn+ ~112 Sn and ~124Sn +~124Sn at 40 and 100 MeV/u. The results indi- cate that N_n is isopsin-dependent as a function of b at both 40 and 100 MeV/u, and Z_bound is also isopsin-dependent at 40 MeV/u but not at 100 MeV/u. Meanwhile, we also discuss how to determine impact parameter of an event at lower and higher incident energies.