Isospin-symmetry breaking corrections for the description of triplet energy differences

The charge-independence breaking of the nuclear interaction is analyzed by means of energy differences among analog states in T=1 isobaric multiplets. Data on triplet energy differences in the sd, pf, and pfg shells, i.e., 18≤A≤66, are reproduced with very good accuracy by large-scale shell-model calculations taking into account, aside from the Coulomb interaction, a single isotensor schematic interaction of monopole-pairing type. It is shown that the effect on the triplet energy differences of this isospin-breaking interaction is of the same magnitude as the Coulomb one. Moreover, its strength is the same for every single-particle orbital of the considered model space.