Density and temperature dependence of nucleon-nucleon elastic cross section
The in-medium neutron-proton, proton-proton (neutron-neutron) elastic scattering cross sections ($σ_{np}^{*}$, $σ_{pp(nn)}^{*}$) are studied based on the effective Lagrangian of density dependent relativistic hadron theory in which the $δ$[$a_0(980)$] meson is included. Our study shows that at low densities the $σ_{np}^*$ is about 3-4 times larger than $σ_{pp(nn)}^*$ and at densities higher than the normal density the isospin effect is almost washed out. Because of coupling to $δ$ meson the $σ_{nn}^*$ and $σ_{pp}^*$ are different in isospin asymmetric medium following the splitting of the proton and neutron mass. The isospin effect on the density dependence of the in-medium nucleon elastic cross section is dominantly contributed by the isovector $δ$ and $ρ$ mesons. The temperature effect on the $σ_{np}^*$ and $σ_{pp(nn)}^*$ is studied. It is shown that the temperature effect is weaker compared with the density effect but it becomes obvious as density increases.