Electric dipole polarizability and the neutron skin

TL;DR

Recent measurements of electric dipole polarizability in lead-208, combined with systematic theoretical calculations, offer new constraints on the neutron skin thickness, impacting nuclear structure and astrophysics understanding.

Contribution

This study assesses the model dependence of the correlation between electric dipole polarizability and neutron skin thickness using diverse density functional theory models.

Findings

The correlation between alphad and rskin is model-dependent and not universal.

Averaging over multiple models provides systematic error estimates for rskin and alphad.

Precise measurements of rskin in 48Ca and 208Pb can significantly constrain nuclear energy density functionals.

Abstract

The recent high-resolution measurement of the electric dipole (E1) polarizability (alphad) in 208Pb [Phys. Rev. Lett. 107, 062502 (2011)] provides a unique constraint on the neutron-skin thickness of this nucleus. The neutron-skin thickness (rskin) of 208Pb is a quantity of critical importance for our understanding of a variety of nuclear and astrophysical phenomena. To assess the model dependence of the correlation between alphad and rskin, we carry out systematic calculations for 208Pb, 132Sn, and 48Ca based on the nuclear density functional theory (DFT) using both non-relativistic and relativistic energy density functionals (EDFs). Our analysis indicates that whereas individual models exhibit a linear dependence between alphad and rskin, this correlation is not universal when one combines predictions from a host of different models. By averaging over these model predictions, we provide estimates with associated systematic errors for rskin and alphad for the nuclei under consideration. We conclude that precise measurements of rskin in both 48Ca and 208Pb---combined with the recent measurement of alphad---should significantly constrain the isovector sector of the nuclear energy density functional.