Investigating the possibility of extracting neutron-skin thickness in nuclei by their collisions at intermediate energies

TL;DR

This study explores whether neutron-skin thickness in nuclei can be inferred from intermediate-energy collisions by analyzing neutron-to-proton yield ratios, revealing sensitivity mainly to collision dynamics rather than initial skin thickness.

Contribution

It demonstrates that the neutron-to-proton yield ratio in intermediate-energy collisions is more influenced by collision dynamics than by initial neutron-skin thickness, providing insights for experimental extraction methods.

Findings

The n/p yield ratio is more sensitive to the symmetry potential than to initial neutron-skin thickness.

Largest effects on n/p ratio occur at high momenta in central collisions at a few GeV/nucleon.

The study suggests limitations in using n/p ratios to directly measure neutron-skin thickness.

Abstract

Inspired by various studies on extracting the density distributions of nuclei from their collisions at ultrarelativistic energies, in the present work we investigate the possibility of extracting the neutron-skin thickness $\Delta r_{np}$ in nuclei by their collisions at intermediate energies. We have analyzed the free neutron-to-proton yield ratio $n/p$ as a candidate probe at both midrapidities and forward rapidities in peripheral and central $^{124}$Sn+$^{124}$Sn collisions based on an isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, and found that the resulting $n/p$ yield ratio is more sensitive to the symmetry potential in the collision dynamics than to the initial $\Delta r_{np}$ in colliding nuclei in most cases. The largest effect on the $n/p$ yield ratio from the initial $\Delta r_{np}$ is observed for nucleons at large transverse or longitudinal momenta in central collisions at the collision energy of a few GeV/nucleon.