With Spin-related Nuclear Nucleon Cross Section And Nuclear Collective Flow

In recent years,the study of the isospin-dependent nuclear physics has rapidly developed, it has become an important scientific frontier. Isospin degree of freedom has a significant impact on the properties of nuclei and nuclear reaction, although both the theoretic and expermental studies have revealed series of the essences of nuclear interaction, some detail information has not yet been clear so far.In order to understand the influence of isospin degree of freedom on the entire nuclear reaction process in the heavy ion collision at the intermediate energy, we first take into account the different reaction systems and also need to consider the impact of the spin distribution, such as the isospin-dependence of nucleon-nucleon cross sections (ie.the in-medium nucleon-nucleon cross sections) and the nuclear symmetry potential et al., At present, people is still relatively poor on the isospin dependence of nucleon-nucleon cross sections research, but it is an important factor in the nuclear reaction dynamics. Because the cross section of nucleon-nucleon collision in isospin dependent medium can not be measured directly, ones usually deduce the information of the crsoss section based on the some theoretical postulation or model. Therefore, there are various forms of it which are used in different transport models.In the dissertation, after comparing the different features of various isospin-denpendent cross section of nucleon nucleon in detail, we study further the influence of the different forms of NN cross sections on the rapidity distributions and the in-plane flows of nucleons in heavy ion collisions induced by neutron-rich nuclei at intermediate energy by using IBUU04transport model with the moment-dependent asymmetry potential. The calculation results indicate that (1) the discrepancies of the rapidity distributions and in-plane flows corresponding to different forms of NN cross sections are large;(2) the sensitivity of the in-plane flow on the NN cross sections is still hold when the new form of moment-dependent asymmetry energy is taken into account;(3) the influence of the N/P ratio of reaction systems on the transverse flow calculated with certain NN cross section is more obvious when the incident energy is near the balance energy.At the same time, the influence of the different forms of NN cross sections on the nuclear stopping is also studied by using IBUU04transport model, the results show that the nuclear stopping is more sensitive on the isospin dependence of NN cross sections, and less affected by symmetry potential; the nuclear stopping power of the different forms of NN cross sections decreases with the increase of the incident energy and is affected impact parameter.