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 $E_{lab}=0.15÷2$ AGeV requires a mean field with strong momentum dependence, i.e. an effective Landau mass $m^{\ast }\simeq 0.68m_0$ 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 ($m^{\ast }\approx 0.62m_0$). All systems investigated are found to be compatible with $m^{\ast }/m_0=0.65\pm 0.03$.

Comments: 22 pages, 13 figures; modified figs. 7,8; added fig. 9; added references