Effect of pairing correlations on the isospin-mixing parameter in deformedN=Zeven-even nuclei

Abstract

Within the particle-number conserving highly truncated diagonalization approach (amounting to a severely truncated shell model built on self-consistent mean-field single-particle states), we investigate the isospin mixing in the ground state of axially deformed even-even $N=Z$ nuclei with $A<80$. The Skyrme interaction in its SIII parametrization is used to generate the self-consistent mean-field solution, whereas the effective residual interaction is approximated by density-independent $\ensuremath{\delta}$ interactions in the $T=0$ and $T=1$ isospin channels. In the correlated ground state of the considered nuclei, the obtained values of the isospin-mixing parameter range from a few tens of a percent to a couple of percents. The pairing correlations in both isospin channels are found to increase a little the isospin-mixing parameter with respect to the Hartree-Fock value by two competing mechanisms. In the $T=0$ channel, isospin mixing is brought mostly by neutron-proton one-pair excitations, whereas in the $T=1$ channel it is essentially generated by the difference between neutron-neutron and proton-proton one-pair excitations.