New phase space calculations for beta-decay half-lives

TL;DR

This paper improves phase space calculations for beta decay by developing a precise Dirac equation solver, including nuclear effects, and updating Q-values, leading to more accurate decay rate predictions crucial for nuclear physics and astrophysics.

Contribution

The authors introduce a new computational method for phase space factors that incorporates realistic nuclear potentials, finite size, screening effects, and updated Q-values, enhancing accuracy over previous approximate methods.

Findings

Close agreement with previous results for positron decay PSFs.

Significant differences in EC PSFs due to screening effects, especially in light nuclei.

Large discrepancies in PSFs when using recent Q-values, impacting decay rate calculations.

Abstract

We revisit the computation of the phase space factors (PSF) involved in the positron decay and electron capture (EC) processes for a large number of nuclei of experimental interest. To obtain the electron/positron wave functions needed in computation, we develop a code for solving accurately the Dirac equation with a nuclear potential derived from a realistic proton density distribution in the nucleus. The finite nuclear size (FNS) and screening effects are included through recipes which differ from those used in previous calculations. Comparing our results with former calculations employing approximate methods but computed with the same Q-values, we find a close agreement for positron decays, while for the EC process there are relevant differences. For the EC process we also find that the screening effect has a notable influence on the computed PSF values specially for light nuclei. Further, we re-computed the same PSF values but using the most recent Q-values reported in literature. In several cases these new Q-values differ significantly from the older ones, which results in large differences in the PSF values as compared with previous results. These new PSF values proposed here, can contribute to a more reliable calculation of the beta decay rates, which are key quantities in the study of nuclei far from the stability line, as well as to better understanding of the stellar evolution.