Isospin Effects of the Mean Field and Two-Body Collision on the Fragmentation Process

Isospin effects of the mean field and two-body collision on the
fragmentation as well as their dependences on the momentum-dependent interaction at intermediate energy heavy ion collisions are studied by using an isospin-dependent quantum molecular dynamics model. We find the prominent isospin effects of the multiplicity of the intermediate mass fragments N_imf, where N_imf depends sensitively on the isospin effect of in-medium nucleon-nucleon cross section and weakly on the variation of symmetry potential in the intermediate energy region. The momentum dependence interaction enhances the sensitivety of N_imf on the isospin effect of two-body collision.