Study of ($p,n$)IAS and ($^3$He,$t$)IAS charge-exchange reactions with the $G$-matrix folding method

Abstract

Differential cross sections of (p, n) and ( 3 He,t) charge-exchange reactions leading to the excitation of the isobaric analog state (IAS) of the target nucleus are calculated with the distorted wave Born approximation. The G-matrix full-folding method is employed to determine the nucleusnucleus optical potential within the framework of the Lane model. G-matrices are obtained from a Brueckner-Hartree-Fock calculation using the Argonne Av18 nucleon-nucleon potential. Target densities have been taken from Skyrme-Hatree-Fock calculations which predict values for the neutron skin thickness of heavy nuclei compatible with current existing data. Calculations are compared with experimental data of the reactions (p, n)IAS on 14 C at E lab = 135 MeV and 48 Ca at E lab = 134 MeV and E lab = 160 MeV, and ( 3 He,t)IAS on 58 Ni, 90 Zr and 208 Pb at E lab = 420 MeV. Experimental results are well described without the necessity of any rescaling of the strength of the optical potential. A clear improvement in the description of the differential cross sections for the ( 3 He,t)IAS reactions on 58 Ni and 90 Zr targets is found when the neutron excess density is used to determine the transition densities. Our results show that the density and isospin dependences of the G-matrices play a non-negligible role in the description of the experimental data.