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

Abstract

We perform a systematic study of in-plane and out-of-plane proton and neutron flow from nucleus-nucleus collisions within the BUU 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 $v_2$ and the in-plane flow $F$ at beam energies $E_{lab} = 0.15 \div 2$ AGeV requires a mean field with strong momentum dependence, i.e. an effective Landau mass $m^* \simeq 0.68 m_0$ at normal nuclear matter density $\rho_0=0.17$ fm$^{-3}$, where $m_0=0.938$ GeV is the bare nucleon mass. Some experimental data on the squeeze-out require an even stiffer momentum dependence ($m^* \approx 0.62 m_0$). All systems investigated are found to be compatible with $m^*/m_0 = 0.65 \pm 0.03$.