Radii of neutron drops probed via the neutron skin thickness of nuclei

TL;DR

This paper establishes a universal linear correlation between neutron drop radii and neutron skin thicknesses in nuclei, enabling model-independent predictions of neutron drop sizes and constraining three-neutron forces, impacting neutron-rich matter studies.

Contribution

It reveals a universal correlation between neutron drop radii and neutron skin thickness, allowing for model-independent radius estimation and improved understanding of neutron interactions.

Findings

Strong linear correlation between neutron drop radii and neutron skin thickness.

Correlation is universal across mean-field models.

Enables model-independent predictions of neutron drop sizes.

Abstract

Multi-neutron systems are crucial to understanding the physics of neutron-rich nuclei and neutron stars. Neutron drops, neutrons confined in an external field, are investigated systematically in both non-relativistic and relativistic density functional theories and with ab initio calculations. We demonstrate a strong linear correlation, which is universal in the realm of mean-field models, between the rms radii of neutron drops and the neutron skin thickness of Pb-208 and Ca-48; i.e., the difference between the neutron and proton rms radii of a nucleus. Due to its high quality, this correlation can be used to deduce the radii of neutron drops from the measured neutron skin thickness in a model-independent way, and the radii obtained for neutron drops can provide a useful constraint for realistic three neutron forces. This correlation, together with high- precision measurements of the neutron skin thicknesses of Pb-208 and Ca-48, will have an enduring impact on the understanding of multi-neutron interactions, neutron-rich nuclei, neutron stars, etc.