Complete electric dipole response and the neutron skin in 208Pb

TL;DR

This paper demonstrates that polarized proton inelastic scattering at very forward angles is an effective method for studying electric dipole and spin magnetic dipole modes in 208Pb, providing insights into neutron skin thickness and nuclear models.

Contribution

It introduces a high-resolution experimental approach to measure electric dipole response and neutron skin in 208Pb, constraining nuclear symmetry energy models.

Findings

Neutron skin thickness in 208Pb is 0.156+0.025-0.021 fm.

The method effectively probes electric dipole and spin magnetic dipole modes.

Results constrain the density dependence of nuclear symmetry energy.

Abstract

A benchmark experiment on 208Pb shows that polarized proton inelastic scattering at very forward angles including 0{\deg} is a powerful tool for high-resolution studies of electric dipole (E1) and spin magnetic dipole (M1) modes in nuclei over a broad excitation energy range to test up-to-date nuclear models. The extracted E1 polarizability leads to a neutron skin thickness r_skin = 0.156+0.025-0.021 fm in 208Pb derived within a mean-field model [Phys. Rev. C 81, 051303 (2010)], thereby constraining the symmetry energy and its density dependence, relevant to the description of neutron stars.