Elliptic flow in intermediate energy heavy ion collisions and n-n interaction and in-medium cross sections

The elliptic flow for Z ≤ 2 particles in heavy ion collisions at energies from several tens to several hundreds MeV per nucleon is investigated by means of transport model,i.e. a new version of the Improved Quantum Molecular Dynamics model (ImQMD05), and compared with experiment results. By applying different Skyrme interactions in transport calculations we have studied the influence of nuclear equation of state(EOS) on the elliptic flow. We find a soft equation of state is required for elliptic flow in intermediate energy heavy ion collisions. The density and energy dependence of in-medium nucleon-nucleon cross sections(NNCS) are studied through the elliptic flow and the nuclear stopping in intermediate energy heavy ion collisions. At low energies, the behavior of in-medium NNCS is similar with phenomenological expression as well as the effective mass scaling, but at higher energies in-medium NNCS are enhanced compared with free ones