Neutron-skin thickness from the study of the anti-analog giant dipole resonance

TL;DR

This study measures the neutron-skin thickness of 124Sn and 208Pb using gamma-decay of the anti-analog giant dipole resonance, combining experimental data with theoretical calculations to achieve precise results.

Contribution

It introduces a novel method that uses AGDR gamma-decay measurements and theoretical RPA calculations to determine neutron-skin thicknesses of isotopes.

Findings

Neutron-skin thickness of 124Sn is 0.175 ± 0.048 fm.

Neutron-skin thickness of 208Pb is 0.181 ± 0.031 fm.

Method offers new possibilities for exotic isotope measurements.

Abstract

The gamma-decay of the anti-analog of the giant dipole resonance (AGDR) has been measured to the isobaric analog state excited in the p(124Sn,n) reaction at a beam energy of 600 MeV/nucleon. The energy of the transition was also calculated with state-of-the-art self-consistent random-phase approximation (RPA) and turned out to be very sensitive to the neutron-skin thickness (\DeltaR_(pn)). By comparing the theoretical results with the measured one, the \DeltaR_(pn) value for 124Sn was deduced to be 0.175 \pm 0.048 fm, which agrees well with the previous results. The energy of the AGDR measured previously for ^(208)Pb was also used to determine the \DeltaR_(pn) for ^(208)Pb. In this way a very precise \DeltaR_(pn) = 0.181 \pm 0.031 neutron-skin thickness has been obtained for 208Pb. The present method offers new possibilities for measuring the neutron-skin thicknesses of very exotic isotopes.