Squeeze-out of nuclear matter in peripheral heavy-ion collisions and momentum-dependent effective interactions

We perform a systematic study of in-plane and out-of-plane proton and neutron flow from nucleus-nucleus collisions within the Boltzmann-Uehling-Uhlenbeck transport approach, employing different parameter sets for the mean-field potentials that can be characterized by the nuclear incompressibility and the stiffness of the momentum-dependent potential. We find that a simultaneous description of the experimental data from the BEVALAC and the SIS on both the nucleon squeeze-out v₂ and the in-plane flow F at beam energies E_lab=0.15-2 A GeV requires a mean field with strong momentum dependence, i.e., an effective Landau mass m^*~=0.68m₀ at normal nuclear matter density ρ₀=0.17 fm^-3, where m₀=0.938 GeV is the bare nucleon mass. Some experimental data on the squeeze-out require an even stiffer momentum dependence (m^*~0.62m₀). All systems investigated are found to be compatible with m^*/m₀=0.65+/-0.03.