Forbidden non-unique ${\beta }^{-}$ transitions and $g_A$-sensitive electron spectral-shapes

Abstract

In the present work, we have done a systematic study of beta decay properties such as electron spectral-shapes, shape factors, and log$ft$ values for the higher forbidden non-unique ${\beta }^{-}$ transitions in the mass region A=85-123. We have performed the nuclear shell model (SM) calculations to explore the sensitivity of the electron spectral-shapes for different axial-vector coupling constants $g_A=0.8-1.27$. The effective interactions GWBXG, G-matrix, SNET and SN100PN are used for different model spaces. In the present work, we have computed the electron spectral-shapes of ${}^{85}$Br, ${}^{87}$Rb, ${}^{93}$Zr, ${}^{97}$Zr, ${}^{101}$Mo, ${}^{115}$Cd, ${}^{117}$Cd, ${}^{119}$In, ${}^{123}$Sn and ${}^{135}$Cs by constraining the small relativistic nuclear matrix element from conserved vector-current hypothesis (CVC). We have found that the electron spectral-shapes are strongly dependent on $g_A$ except the second forbidden non-unique ${\beta }^{-}$ transition ${}^{93}$Zr.

Comments: 12 pages, 4 figures, and 3 tables; Physical Review C (2025)