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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 is
Effect of isospin dependence of nucleon-nucleon (NN) cross section σNNiso 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 In heavy ion collisions. Where the isospin independent NN cross sections? 1noiso and? 2noiso are defined as? nnn =? pp =? np (? 1noiso) and? nn =? pp = (1/2) (? np +? nn) -medium NN cross section is