相对论重离子反应的热化过程

本文从相对论BUU理论出发研究了1GeV/n能区重离子反应全局(global)和局域(local)平衡性质,计算表明在该能区平均场对反应动力学过程仍有相当的作用;对有限核系统的反应动力学过程的时间演化的研究表明,有限核系统无论全局的还是局域的平衡均未能达到完全平衡,因而对有限核系统重离子反应基于完全热平衡概念的适用性值得怀疑.     

△共振态的硬过程及软过程产生截面在同位旋不对称核体系下的介质修正研究

基于一个相对论的BUU方法,研究了△共振态的硬过程（NN → N△）及软过程（Nπ → △）产生截面及△的衰变宽度在同位旋不对称核体系下的介质修正（包括能量、密度、特别是同位旋依赖的）效应。发现类似于核子-核子弹性散射过程,△硬过程产生截面的密度修正及在同位旋不对称体系下的质量劈裂效应都比较强烈,而△的软过程产生截面及衰变宽度的密度依赖和质量劈裂效应都相对较弱。对硬过程,其截面最大的劈裂效应出现在△++和△-的产生道中,而对软过程,△++和△-的产生道中的劈裂效应则最小且与硬过程的相反。Within the framework of the relativistic BUU approach, we investigate the effect of energy-, density-, and especially isospin-dependent medium modifications on △ production cross sections of both hard (NN → N△) and soft (Nπ → △) processes as well as its decay width. It is found that, similar to the nucleon-nucleon elastic scattering, the △ production cross section from the hard process is strongly dependent on both density and the mass splitting effect in the isospin asymmetric matter. While the dependence is relative weak from the soft one, and so is the △ decay width. Further, in the hard (soft) process, the splitting effect is largest (smallest) and of opposite sign for the △++ and △- states.