Effect of Isospin Dependence of Nucleon-nucleon Cross Section on Isospin Fractionation Ratio as Increase of Neutron-proton Ratio of Collision System

摘要

Effect of isospin dependence of nucleon-nucleon (N-N) cross sectionσNNiso on the isospin fractionation ratio (n/p)free/(n/p)liq as the increase of neutron-proton ratio of collision system (n/p)sys is investigated in heavy ion collisions. Where the isospin independent N-N cross sectionsσ1noiso andσ2noiso are defined asσnn=σpp =σnp(σ1noiso) andσnn=σpp=(1/2) (σnp+σnn)(σ2noiso) respectively. An empirical density dependent expression of the in-medium N-N cross section