Measuring neutron skin by grazing isobaric collisions

TL;DR

This paper proposes a novel method to directly measure neutron skin thickness in nuclei using net-charge multiplicities in ultra-peripheral isobaric collisions, aiming to reduce theoretical uncertainties in nuclear physics and astrophysics.

Contribution

It introduces a new approach for direct measurement of neutron skin thickness via grazing isobaric collisions, complementing previous indirect methods.

Findings

Demonstrated the feasibility using TRENTO and URQMD models.

Showed sensitivity of net-charge multiplicities to neutron skin thickness.

Proposed a simpler superimposition model for analysis.

Abstract

Neutron skin thickness ($\Delta r_{\rm np}$) of nuclei and the inferred nuclear symmetry energy are of critical importance to nuclear physics and astrophysics. It is traditionally measured by nuclear processes with significant theoretical uncertainties. We recently proposed an indirect measurement of the $\Delta r_{\rm np}$ by charged hadron multiplicities in central isobaric collisions at relativistic energies, which are sensitive to nuclear densities. In this Letter, we propose a direct measurement of the $\Delta r_{\rm np}$ by using net-charge multiplicities in ultra-peripheral (grazing) collisions of those isobars, under the assumption that they are simple superimposition of nucleon-nucleon interactions. We illustrate this novel approach by the TRENTO and URQMD models.