Competition of deformation and neutron-proton pairing in Gamow-Teller transitions for ^(56, 58)Ni and ^(62,64)Ni

We investigated effects of neutron-proton ($np$) pairing correlations comprising isoscalar (IS) and isovector (IV) component on Gamow-Teller (GT) transitions of $^{56, 58,62,64}$Ni by taking into account nuclear deformation in a deformed Woods-Saxon mean field. Our GT calculations based on a deformed Bardeen-Cooper-Schriffer (DBCS) approach have been performed within a deformed quasi-particle random phase approximation (DQRPA) which explicitly includes the deformation as well as all kinds of pairing correlations not only at the DBCS but also at the DQRPA stage. Competition of these two effects, the deformation and the IS spin-triplet and IV spin-singlet component of the $np$ pairing, is shown to be significant for understanding the GT strength distributions of Ni isotopes.