Momentum dependence of the symmetry potential and its influence on nuclear reactions

TL;DR

This paper introduces a momentum-dependent symmetry potential in a nuclear reaction model, revealing its significant impact on isospin-sensitive observables in heavy-ion collisions, especially at high momenta.

Contribution

It is the first implementation of a Skyrme-type momentum-dependent force with isospin effects in the LQMD model, highlighting the importance of momentum dependence in symmetry potentials.

Findings

Different distributions of observables with and without momentum dependence.

High transverse momentum neutron/proton ratios are sensitive to momentum dependence.

Excitation functions of certain particle yield ratios are affected by the symmetry potential's momentum dependence.

Abstract

A Skyrme-type momentum-dependent nucleon-nucleon force distinguishing isospin effect is parameterized and further implemented in the Lanzhou Quantum Molecular Dynamics (LQMD) model for the first time, which leads to a splitting of nucleon effective mass in nuclear matter. Based on the isospin- and momentum-dependent transport model, we investigate the influence of momentum-dependent symmetry potential on several isospin-sensitive observables in heavy-ion collisions. It is found that symmetry potentials with and without the momentum dependence but corresponding to the same density dependence of the symmetry energy result in different distributions of the observables. The mid-rapidity neutron/proton ratios at high transverse momenta and the excitation functions of the total $\pi^{-}/\pi^{+}$ and $K^{0}/K^{+}$ yields are particularly sensitive to the momentum dependence of the symmetry potential.