Impact of first-forbidden transitions in gross theory of beta decay model on r-process nuclei

Recently, a new version of the Gross Theory of β β -decay (GTBD) was proposed with the aim of providing more accurate predictions for the energy peak of the Gamow-Teller resonance and a new minimization procedure to reproduce the experimental half-lives [1]. In this work, we have incorporated the first-forbidden (FF) transitions and the Weizsäcker-Skyrme (WS4) mass formula into this version of the GTBD. We evaluated the impact of these transitions on nuclei involved in the r -process, with special emphasis on nuclei with magic neutron numbers, which are crucial for determining the elemental abundances. The impact of FF transitions is found to be more pronounced in even-odd and odd-even nuclei, although modest improvements are also observed in even-mass nuclei. For nuclei with magic neutron numbers, we quantified the uncertainty originating from nuclear masses. Based on these results, we defined a GTBD uncertainty region where the experimental data of the waiting-point nuclei are successfully reproduced within this region.