Updated evaluation of potential ultra-low Q value $\beta$-decay candidates

TL;DR

This paper updates the list of potential ultra-low Q value beta decay candidates by analyzing atomic mass and nuclear energy data, highlighting the need for more precise measurements to confirm their suitability for neutrino mass experiments.

Contribution

It provides an updated evaluation of candidate isotopes for ultra-low Q value beta decay based on recent atomic and nuclear data, emphasizing the importance of precise mass measurements.

Findings

Identification of new potential ultra-low Q value beta decay candidates

Highlighting the need for more precise atomic mass measurements

Providing a prioritized list for future experimental verification

Abstract

"Ultra-low" Q value $\beta$ decays are referred to as such due to their low decay energies of less than $\sim$1 keV. Such a low energy decay is possible when the parent nucleus decays into an excited state in the daughter, with an energy close to that of the Q value. These decays are of interest as potential new candidates for neutrino mass determination experiments and as a testing ground for studies of atomic interference effects in the nuclear decay process. In this paper, we provide an updated evaluation of atomic mass data and nuclear energy level data to identify potential ultra-low Q value $\beta$ decay candidates. For many of these candidates, more precise and accurate atomic mass data is needed to determine if the Q value of the potential ultra-low decay branch is energetically allowed and in fact ultra-low. The precise atomic mass measurements can be achieved via Penning trap mass spectrometry.