Density and temperature dependence of nucleon-nucleon elastic cross section

The in-medium neutron-proton, proton-proton (neutron-neutron) elastic scattering cross sections (σₙₚ*,σₚₚ₍ₙₙ₎*) are studied based on the effective Lagrangian of density dependent relativistic hadron theory in which the δ[a₀(980)] meson is included. Our study shows that at low densities the σₙₚ* is about three to four times larger than σₚₚ₍ₙₙ₎* and at densities higher than the normal density the isospin effect is almost washed out. Because of coupling to δ meson the σₙₙ* and σₚₚ* are different in isospin asymmetric medium following the splitting of the proton and neutron masses. 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 σₙₚ* and σₚₚ₍ₙₙ₎* is studied. It is shown that the temperature effect is weaker compared with the density effect but it becomes obvious as density increases.