THE IN-MEDIUM NUCLEON-NUCLEON CROSS-SECTION AND BUU SIMULATIONS OF HEAVY-ION REACTIONS

The in-medium nucleon-nucleon cross section is calculated microscopically starting from the thermodynamic T-matrix at finite temperatures. We find pronounced deviations from the elementary free-space NN cross section. The sources of these deviations, Pauli blocking and self-energy contributions, are discussed separately. We present a Boltzmann-Uehling-Uhlenbeck computer simulation of heavy-ion reactions at intermediate energies where the in-medium cross section is incorporated into the collision term. The solution of the BUU equation at different beam energies gives an estimate of how the number of collisions during the heavy-ion reaction is changed by medium corrections to the NN cross section. The influence of these medium corrections on the number of collisions in the heavy-ion reaction is discussed.