PROBING THE MOMENTUM-DEPENDENT MEDIUM MODIFICATIONS OF THE NUCLEON–NUCLEON ELASTIC CROSS SECTION

The momentum dependence of the medium modifications on nucleon–nucleon elastic cross sections is investigated with the microscopic transport model UrQMD. The semi-peripheral Au+Au collision at the beam energy Eb = 400A MeV is adopted as an example. It is found that uncertainties of the momentum dependence on medium modifications of cross sections visibly influence the yield and collective flow distributions of free nucleons. In these observables, the elliptic flow is sensitively dependent on detailed forms of the momentum dependence. However, it is weakly influenced by the splitting effect of the neutron–neutron and proton–proton cross sections.