Neutron skin thickness of 116,118,120,122,124Sn determined from reaction cross sections of proton scattering

Abstract

Background:The cross sections of the isovector spin-dipole resonances (SDR) in the Sb isotopes have been measured. Within the model used, the neutron-skin thicknesses rskin(exp) deduced 0.12±0.06 fm for 116Sn, 0.13±0.06 fm for 118Sn, 0.18±0.07 fm for 120Sn, 0.22±0.07 fm for 122Sn, 0.19±0.07 fm for 124Sn. We tested the chiral (Kyushu) g-matrix folding model for 12C+12C scattering, and found that the Kyushu g-matrix folding model is reliable for reaction cross sections σR in 30˜<Ein˜<100MeV and 250˜<Ein˜<400MeV. We determine neutron skin thickness rskin(exp), using measured σR of 4He+116,120,224Sn scattering. The results are rskin(exp)=0.242±0.140 fm for 116Sn, rskin(exp)=0.377±0.140 fm for 120Sn, rskin(exp)=0.180±0.142 fm for 124Sn. The σR are available for proton scattering on 116,118,120,122,124Sn with high accuracy of 2∼3% as a function of incident energy Ein. Purpose:Our aim is to determine rskin(exp) for 116,118,120,122,124Sn with small errors by using the Kyushu g-matrix folding model. Methods:Our model is the Kyushu g-matrix folding model with the densities scaled from the D1S-GHFB+AMP neutron density, where D1S-GHFB+AMP stands for Gogny-D1S HFB (D1S-GHFB) with the angular momentum projection (AMP). Results:The proton radii of D1S-GHFB+AMP agree with those calculated with the isotope shift method based on the electron scattering. We then scale the D1S-GHFB+AMP neutron densities so as to reproduce the σR(exp). In 30˜<Ein˜<65MeV, we determine rskin(exp) from measured σR. The values are rskin(exp)=0.118±0.021 fm for 116Sn, 0.112±0.021 fm for 118Sn, 0.124±0.021 fm for 120Sn, 0.156±0.022 fm for 124Sn. As for 122Sn, the skin value in 30˜<Ein˜<50MeV is 0.122±0.024 fm. Conclusions:Our results are consistent with the previous values.