Charge, neutron, and weak size of the atomic nucleus

TL;DR

This paper presents an ab initio calculation of the neutron distribution in calcium-48, revealing a smaller neutron skin than previously believed and providing insights relevant to nuclear physics and neutron star properties.

Contribution

The study offers the first ab initio calculation of neutron distribution in calcium-48, constraining neutron skin size and predicting related measurable quantities.

Findings

Neutron skin in calcium-48 is smaller than earlier estimates.

Predicted electric dipole polarizability and weak form factor match upcoming measurements.

Results provide constraints on neutron star size based on nuclear data.

Abstract

What is the size of the atomic nucleus? This deceivably simple question is difficult to answer. While the electric charge distributions in atomic nuclei were measured accurately already half a century ago, our knowledge of the distribution of neutrons is still deficient. In addition to constraining the size of atomic nuclei, the neutron distribution also impacts the number of nuclei that can exist and the size of neutron stars. We present an ab initio calculation of the neutron distribution of the neutron-rich nucleus $^{48}$Ca. We show that the neutron skin (difference between radii of neutron and proton distributions) is significantly smaller than previously thought. We also make predictions for the electric dipole polarizability and the weak form factor; both quantities are currently targeted by precision measurements. Based on ab initio results for $^{48}$Ca, we provide a constraint on the size of a neutron star.