Medium modifications of the nucleon-nucleon elastic cross section in neutron-rich intermediate energy HICs

Several observables of unbound nucleons which are to some extent sensitive to the medium modifications of nucleon-nucleon elastic cross sections in neutron-rich intermediate energy heavy ion collisions are investigated. The splitting effect of neutron and proton effective masses on cross sections is discussed. It is found that the transverse flow as a function of rapidity, the Qzz as a function of momentum, and the ratio of halfwidths of the transverse to that of longitudinal rapidity distribution Rt/l are very sensitive to the mediummodifications of the cross sections. The transverse momentum distribution of correlation functions of two-nucleons does not yield information on the in-medium cross section. PACS numbers: 25.70.-z, 24.10.Lx, 25.75.-q ∗ Fellow of the Alexander von Humboldt Foundation.