Ab initio predictions link the neutron skin of ${}^{208}$Pb to nuclear forces

TL;DR

This paper uses advanced quantum many-body methods and statistical tools to predict the neutron skin thickness of ${}^{208}$Pb from fundamental nuclear forces, linking nuclear structure to neutron star properties.

Contribution

It introduces a novel combination of ab initio calculations, statistical analysis, and emulator technology to accurately predict properties of a heavy nucleus from first principles.

Findings

Predicted neutron skin thickness of ${}^{208}$Pb is smaller and more precise than previous measurements.

Demonstrated the role of realistic nuclear forces in heavy nuclei.

Established a link between nuclear forces and neutron star properties.

Abstract

Heavy atomic nuclei have an excess of neutrons over protons, which leads to the formation of a neutron skin whose thickness is sensitive to details of the nuclear force. This links atomic nuclei to properties of neutron stars, thereby relating objects that differ in size by orders of magnitude. The nucleus ${}^{208}$Pb is of particular interest because it exhibits a simple structure and is experimentally accessible. However, computing such a heavy nucleus has been out of reach for ab initio theory. By combining advances in quantum many-body methods, statistical tools, and emulator technology, we make quantitative predictions for the properties of ${}^{208}$Pb starting from nuclear forces that are consistent with symmetries of low-energy quantum chromodynamics. We explore $10^9$ different nuclear-force parameterisations via history matching, confront them with data in select light nuclei, and arrive at an importance-weighted ensemble of interactions. We accurately reproduce bulk properties of ${}^{208}$Pb and determine the neutron skin thickness, which is smaller and more precise than a recent extraction from parity-violating electron scattering but in agreement with other experimental probes. This work demonstrates how realistic two- and three-nucleon forces act in a heavy nucleus and allows us to make quantitative predictions across the nuclear landscape.