Beyond-mean-field calculations of allowed and first-forbidden $\beta^-$ decays of $r$-process waiting-point nuclei

TL;DR

This paper presents advanced relativistic calculations of beta-decay half-lives for neutron-rich nuclei at N=82 and N=126, including allowed and first-forbidden transitions, to improve understanding of heavy-element nucleosynthesis.

Contribution

It introduces a beyond-mean-field approach incorporating quasiparticle-vibration coupling for more accurate beta-decay rate predictions of r-process nuclei.

Findings

Quasiparticle-vibration coupling enhances Gamow-Teller contributions near stability.

First-forbidden transitions dominate decay at N=126, even with vibrational coupling.

Calculated half-lives show improved agreement with experimental data.

Abstract

$\beta$-decay rates of neutron-rich nuclei, in particular those located at neutron shell closures, play a central role in simulations of the heavy-element nucleosynthesis and resulting abundance distributions. We present $\beta$-decay half-lives of even-even $N=82$ and $N=126$ $r$-process waiting-point nuclei calculated in the approach based on relativistic quasiparticle random phase approximation with quasiparticle-vibration coupling. The calculations include both allowed and first-forbidden transitions. In the $N=82$ chain, the quasiparticle-vibration coupling has an important impact close to stability, as it increases the contribution of Gamow-Teller modes and improves the agreement with the available data. In the $N=126$ chain, we find the decay to proceed dominantly via first-forbidden transitions, even when the coupling to vibrations is included.