Effects of Residual Tensor and Pairing Forces on the Gamow-Teller states in Magic Nuclei, 48Ca, 90Zr, 132Sn, and 208Pb

Abstract

We investigate the effects of residual tensor force (TF) and pairing force on the Gamow-Teller (GT) transitions in four magic nuclei, Ca-48, Zr-90, Sn-132 and Pb-208. The TF is taken into account by using the Br & uuml;ckner G-matrix theory with the charge-dependent (CD) Bonn potential as the residual interaction of charge-exchange quasiparticle random phase approximation (QRPA). We found that particle-particle (p-p) tensor interaction does not affect the GT transitions because of the closed shell nature in the nuclei, but repulsive particle-hole (p-h) residual interaction for the p-h configuration of spin-orbit partners dominates the high-lying giant GT states for all of the nuclei. It is also shown that appreciable GT strengths are shifted to a lower energy region by the attractive p-h TF for the same j(pi) = j(nu) configuration, and produce the low-lying GT peak about 2.5 MeV in Ca-48. Simultaneously, in Zr-90 and Sn-132, the low-energy GT strength appears as a lower energy shoulder near the main GT peak. On the other hand, the shift of the low-lying GT state is not seen clearly for Pb-208 because of the strong spin-orbit splitting of high j orbits, which dominates the GT strength.