Isospin dependence of nucleon-nucleon elastic cross section

Abstract

The in-medium neutron-proton, proton-proton (neutron-neutron) scattering cross sections $({\ensuremath{\sigma}}_{\mathrm{np}}^{*},$ ${\ensuremath{\sigma}}_{\mathrm{pp}(\mathrm{nn})}^{*})$ are studied based on QHD-II type Lagrangian within the framework of the microscopic transport theory. The results demonstrate that, for free nucleon-nucleon scattering cross sections, the isospin dependence is dominantly caused by the $\ensuremath{\rho}$ meson field. The medium correction of nucleon-nucleon scattering cross sections is also isospin dependent, ${\ensuremath{\sigma}}_{\mathrm{np}}^{*}$ depends on the baryon density weakly and ${\ensuremath{\sigma}}_{\mathrm{pp}(\mathrm{nn})}^{*}$ depends on the baryon density significantly, which is due to the different effects of the medium correction of nucleon mass and $\ensuremath{\rho}$ meson mass on ${\ensuremath{\sigma}}_{\mathrm{np}}$ and ${\ensuremath{\sigma}}_{\mathrm{pp}(\mathrm{nn})},$ respectively.