Ab initio computations of the fourth-order charge density moments of $^{48}$Ca and $^{208}$Pb

TL;DR

This study uses ab initio calculations to analyze the fourth-order charge density moments of $^{48}$Ca and $^{208}$Pb, revealing strong correlations with charge and neutron radii but weak links to neutron skin, impacting experimental approaches.

Contribution

It provides the first ab initio predictions of fourth-order charge density moments for these nuclei, clarifying their relation to nuclear radii and neutron skin.

Findings

Strong correlation between $R_{ch}^4$ and charge/neutron radii

Weak correlation between $R_{ch}^4$ and neutron skin

Limits on using electron scattering to determine neutron skin

Abstract

Neutron skins of neutron-rich nuclei connect nuclei with the matter in neutron stars. High-precision measurements of nuclear charge densities to extract higher-order moments are proposed to be sensitive to neutron radii and skin thicknesses. We investigate the charge density of $^{48}$Ca and $^{208}$Pb, leading candidates for such studies, with ab initio nuclear structure calculations. We find strong correlations between the fourth-order charge density moment $R_\mathrm{ch}^4$ and the charge and neutron radii, allowing us to predict $R_\mathrm{ch}^4$ for $^{48}$Ca and $^{208}$Pb. We find a substantially weaker correlation between the fourth-order charge density moment and the neutron skin, limiting the ability of high-precision electron scattering to determine the neutron skin in a model-independent manner.