Effective Nucleon Masses from Heavy Ion Collisions

TL;DR

This study investigates the momentum dependence of the isovector mean-field potential in heavy ion collisions, providing experimental data that constrains theoretical models of nucleon effective masses.

Contribution

It offers precise experimental measurements of neutron and proton spectra that distinguish between different momentum dependencies of the symmetry mean-field potential.

Findings

Small differences between neutron and proton effective masses.

Experimental data discriminates between various momentum dependencies.

Model calculations align with observed spectra.

Abstract

We probe the momentum dependence of the isovector mean-field potential by comparing the energy spectra of neutrons and protons emitted in $^{112}$Sn+$^{112}$Sn and $^{124}$Sn+$^{124}$Sn collisions at incident energies of E/A=50 and 120 MeV. We achieve experimental precision that discriminates between different momentum dependencies for the symmetry mean-field potential. Comparisons of the experimental results to Improved Quantum Molecular Dynamics model calculations with Skyrme Interactions indicate small differences between the neutron and proton effective masses.