Origin of transverse momentum in relativistic heavy-ion collisions: Microscopic study

We study the origin of the transverse momentum distribution in heavy-ion collisions within a relativistic transport approach. To achieve a better understanding of the reaction dynamics, we decompose the total ${\mathit{p}}_{\mathit{t}}$ distribution into a mean-field, N-N collision, and Fermi-momentum part. We find that the origin of the transverse momentum strongly depends on the rapidity region. Our investigation of the impact-parameter and mass dependence suggests that peripheral collisions may be useful to investigate the momentum dependence of the mean-field in the nucleus-nucleus case, whereas the mass dependence could give hints about the N-N-collision part. Only after these two issues are settled it may be possible to extract information about the density dependence in central collisions, which may, however, necessitate reactions at even higher energies than the 800 MeV/nucleon considered in this work.