Elimination of influence of neutron-skin size difference of initial colliding nuclei in Pb+Pb collisions

TL;DR

This study demonstrates that combining specific neutron-proton flow observables can effectively remove the influence of initial neutron-skin size differences in Pb+Pb collisions, enhancing the probing of nuclear symmetry energy.

Contribution

The paper introduces a method using combined neutron-proton flow observables to eliminate neutron-skin size effects in heavy-ion collision analyses.

Findings

Neutron-proton differential elliptic flow effectively removes neutron-skin effects.

Neutron-proton transverse flow difference is sensitive to symmetry energy.

Combined neutron-proton stopping power shows sensitivity at lower energies.

Abstract

Within an isospin- and momentum-dependent transport model using as an input nucleon density profiles from Hartree-Fock calculations based on a modified Skyrme-like (MSL) model, we study how to eliminate the influence of neutron-skin size difference of initial colliding nuclei in probing the nuclear symmetry energy. Within the current experimental uncertainty range of neutron-skin size of $^{208}$Pb, the Pb+Pb collisions are performed in semicentral and peripheral collisions with impact parameters of 5 and 9fm and at beam energies from 50 MeV/nucleon to 1000 MeV/nucleon, respectively. It is shown that combination of neutron and proton collective flows, i.e., neutron-proton differential elliptic flow, neutron-proton elliptic flow difference, neutron-proton differential transverse flow and neutron-proton transverse flow difference, can effectively eliminate the effects of neutron-skin size difference and thus can be as useful sensitive observables in probing nuclear matter symmetry energy in heavy-ion collisions. Moreover, the combined neutron-proton stopping power including the neutron-proton differential stopping power and neutron-proton stopping power difference can also eliminate the effects of neutron-skin size difference and shows some sensitivities to symmetry energy especially at the lower beam energy.