EFFECTS OF PAIRING CORRELATIONS ON THE ISOSPIN-SYMMETRY-BREAKING CORRECTION TO SUPER-ALLOWED 0+ → 0+ FERMI TRANSITIONS WITHIN THE HIGHER TAMM–DANCOFF APPROACH

Super-allowed 0+ → 0+ Fermi transitions provide a test at low energy of the Standard Model of elementary interactions. The isospin-symmetry breaking due to the electromagnetic interaction at a nuclear level is a fundamental theoretical tool for the understanding of weak processes beyond the Standard Model. Within the Higher Tamm–Dancoff description of correlated nuclear states, we calculate the isospin-symmetry breaking correction δc to the Fermi transition matrix element. A sensitivity study on the T = 0 pairing correlations is carried out and some tests of model ingredients are performed. The obtained correction is of the order of 0.15~0.2% for plausible strengths in the T = 1 and T = 0 channels of the residual interaction. This is expected to constitute a lower bound.