Constraining the density slope of nuclear symmetry energy at subsaturation densities using electric dipole polarizability in $^{208}$Pb

TL;DR

This paper uses electric dipole polarizability measurements in lead-208 to tightly constrain the density slope of the nuclear symmetry energy at subsaturation densities, impacting nuclear structure and neutron star models.

Contribution

It demonstrates the sensitivity of electric dipole polarizability in lead-208 to the symmetry energy slope at subsaturation density and extracts a precise value for this parameter.

Findings

Determined the slope parameter L at 0.11 fm$^{-3}$ as 47.3 ± 7.8 MeV.

Linked the symmetry energy slope to neutron skin thickness and neutron star transition density.

Provided a new constraint on nuclear matter properties at subsaturation densities.

Abstract

Nuclear structure observables usually most effectively probe the properties of nuclear matter at subsaturation densities rather than at saturation density. We demonstrate that the electric dipole polarizibility $\alpha _ {\text{D}}$ in $^{208}$Pb is sensitive to both the magnitude $E_{\text{sym}}(\rho_{\text{c}})$ and density slope $L(\rho_{\text{c}})$ of the symmetry energy at a subsaturation cross density $\rho_{\text{c}} = 0.11$ fm$^{-3}$. Using the experimental data of $\alpha _ {\text{D}}$ in $^{208}$Pb from RCNP and the recent accurate constraint of $E_{\text{sym}}(\rho_{\text{c}})$ from the binding energy difference of heavy isotope pairs, we extract a value of $L(\rho_{\text{c}}) = 47.3 \pm 7.8$ MeV. The implication of the present constraint of $L(\rho_{\text{c}})$ to the symmetry energy at saturation density, the neutron skin thickness of $^{208}$Pb and the core-crust transition density in neutron stars is discussed.