Understanding the mirror asymmetry in Gamow-Teller transition rates between Al 28 (β-) Si 28m and P 28 (β+) Si 28m

The long-standing discrepancy between shell-model and experimental values of the mirror asymmetry in Gamow-Teller transition rates for Al28(β-)Si28m and P28(β+)Si28m is partially resolved by integrating the p-orbital contribution into the radial mismatch correction term. This approach offers a potential estimate of the radial mismatch-induced core-orbital contribution based on the French-Macfarlane sum rules, avoiding the need for heavy calculations required by the first-principle shell model. Additionally, the isospin-mixing contribution undergoes considerable improvement through scaling the calculated isospin-mixing correction with the experimental energy separation between the lowest two admixed states, in accordance with results from the two-level model.