Constraints on the Nuclear Symmetry Energy from Experiments, Theory and Observations

TL;DR

This paper reviews experimental, theoretical, and observational constraints on nuclear symmetry energy parameters, highlighting recent measurements and their consistency with neutron matter predictions and astrophysical data.

Contribution

It synthesizes diverse constraints on symmetry energy parameters and demonstrates their mutual consistency, especially with recent neutron skin and neutron star observations.

Findings

Joint constraints from PREX and CREX yield J=32.2±1.7 MeV and L=52.9±13.2 MeV.

Neutron skin measurements agree with neutron matter predictions.

Astrophysical observations like NICER and GW170817 support these constraints.

Abstract

Nuclear mass measurements and neutron matter theory tightly constrain the nuclear symmetry energy parameters $J$, $L$, $K_{sym}$ and $Q_{sym}$. Corroboration of these constraints on $J$ and $L$ can be found from measurements of the neutron skin thicknesses and dipole polarizabilities of neutron-rich nuclei. The experimental constraints on these parameters are compared with those obtained from consideration of astrophysical measurements of the neutron star radius, which we show is highly correlated with $L$. Attention is aimed at the recent PREX and CREX neutron skin measurements from Jefferson Lab, NICER neutron star radius measurements, and a new interpretation of the GW170817 tidal deformability measurement. We find joint satisfaction of PREX and CREX gives $J=32.2\pm1.7$ MeV and $L=52.9\pm13.2$ MeV, in excellent agreement with neutron matter predictions of $J=32.0\pm1.1$ MeV and $L=51.9\pm7.9$ MeV.