Probing small neutron skin variations in isotope pairs by hyperon-antihyperon production in antiproton--nucleus interactions

TL;DR

This paper introduces a novel method using antiproton-induced hyperon-antihyperon production near threshold to measure neutron skin variations across isotopes, validated by transport model simulations.

Contribution

It proposes a new experimental approach linking hyperon production ratios to neutron skin thickness changes, supported by detailed transport model calculations.

Findings

Strong correlation between double ratio and neutron skin variation.

Method sensitive to small neutron skin differences.

Validated approach with GiBUU simulations across isotopes.

Abstract

We propose a new method to study the evolution of the neutron periphery between different isotopes by considering antiproton--nucleus interactions close to the production threshold of $\Lambda \overline{\Lambda }$ and $\Sigma^-\overline{\Lambda }$ pairs. At low energies, $\Lambda \overline{\Lambda }$ pairs are produced in $\overline{\text{p}} +\text{p}$ collisions, while $\Sigma^-\overline{\Lambda }$ pairs can only be produced in $\overline{\text{p}} +\text{n}$ interactions. Within a simple geometrical picture we show that the double ratio for the production of $\Sigma^-\overline{\Lambda }$ and $\Lambda \overline{\Lambda }$ pairs for two different isotopes are related to the variation of the neutron skin thickness between the two nuclei. Performing high statistics calculations with the Gie\ss en Boltzmann--Uehling--Uhlenbeck (GiBUU) transport model for several isotope pairs covering a wide range of elements we verify a strong correlation between the double ratio from the full transport simulations and the schematic model. This correlation enables us to quantify the potential of the proposed method for precise studies of neutron skin variations in isotope chains.