Isospin nonconservation in sd-shell nuclei

The question of isospin-symmetry breaking in nuclei of the sd shell is addressed. We propose a new global parametrization of the isospin-nonconserving shell-model Hamiltonian which accurately describes experimentally known isobaric mass splittings. The isospin-symmetry violating part of the Hamiltonian consists of the Coulomb interaction and effective charge-dependent forces of nuclear origin. Particular attention has been paidtotheeffectoftheshort-rangecorrelations.Thebehaviorof band ccoefficientsoftheisobaric-mass-multiplet equation (IMME) is explored in detail. In particular, a high-precision numerical description of the staggering effect is proposed and contribution of the charge-dependent forces to the nuclear pairing is discussed. The Hamiltonian is applied to the study of the IMME beyond a quadratic form in the A = 32 quintet, as well as to calculation of nuclear structure corrections to superallowed 0 + → 0 + Fermi β decay and to amplitudes of Fermi transitions to nonanalog states in sd-shell nuclei.