中能重离子碰撞中多重碎裂的同位旋效应  

Isospin Effect in Multifragmentation Process of Heavy Ion Collisions at Intermediate Energy

作　　者：赵强[2] 刘建业[1,2] 张丰收[1,2] 王顺金[1] 左维[2] 孙列文 

机构地区：[1]中国科学院近代物理研究所,兰州730000 [2]兰州重离子加速器国家实验室原子核理论中心,兰州730000

出　　处：《高能物理与核物理》2000年第11期1024-1029,共6页High Energy Physics and Nuclear Physics

基　　金：国家自然科学基金(19775057,19847002,19775020);中国科学院基金

摘　　要：利用同位旋相关的量子分子动力学， 研究了逆反应系统１２０ Ｘｅ＋４０Ｃａ， １２０Ｃｄ＋４０Ａｒ和７６Ｋｒ＋４０Ｃａ，７６Ｚｎ＋４０Ａｒ中多重碎裂的 同位旅效应．对于在中能区 缺中子碰撞系统的中等质量碎片多重性大于丰中子碰撞系统的现象进行了分析 和讨论．From the simulation of intermediate energy heavy ion collisions by using the isospin dependent quantum molecular dynamics (IQMD), we have investigated the isospin effects on the multifragmentation process in intermediate energy heavy ion collisions: reverse reactions 120Xe + 40Ca, 120Cd+ 40Ar, 76Kr + 40Ca and 76Zn + 40Ar. To describe isospin effects appropriately, QMD was modified properly. The density dependent mean field contains correct isospin term including symmetry energy and Coulomb potential. The in-medium n-n cross section is different for neuron-neutron (proton-proton) and neutron-proton collisions. And finally Pauli blocking was counted by distinguishing neutrons and protons. In addition, the initial condition of the ground state of two colliding nuclei also contains isospin information. The calculated results show a prominent isospin effects for the multifragmentation process among the colliding systems with different neutron or proton excess. The correlation between Nimf and Nc for neutron-deficient systems are always larger than those for neutron-rich systems in intermediate energy region for all of colliding systems studied here, and the mechanism causing the above isospin effects is mainly due to the fact that the mean n-n cross section for the neutron-rich system is smaller than that of neutron-deficient system. Thus one can combine experimental studies and theoretical simulations to investigate the isospin effect of multi fragmentation Process and to extract the information on isospin dependence of in-medium n-n cross section from the correlation between Nimf and Nc.

关 键 词：同位旋效应 中等质量碎片多重性 核子-核子碰撞截面 

分 类 号：O571[理学—粒子物理与原子核物理]