High-precision $Q_{EC}$-value measurement of the superallowed $\beta^+$ emitter $^{22}$Mg and an evaluation of the $A=22$ isobaric triplet

TL;DR

This paper reports the most precise measurement of the $Q_{EC}$-value for $^{22}$Mg and presents ab-initio shell-model calculations of the $A=22$ isobaric triplet, advancing the understanding of superallowed beta decays.

Contribution

It provides the most precise $Q_{EC}$ measurement for $^{22}$Mg and introduces first-principles shell-model calculations of the $A=22$ IMME using the in-medium similarity renormalization group.

Findings

$Q_{EC}$ value measured as 4781.40(22) keV.

Ab-initio calculations show good agreement with experimental data.

Demonstrates potential for reliable first-principles ISB correction calculations.

Abstract

A direct $Q_{EC}$-value measurement of the superallowed $\beta^+$ emitter $^{22}$Mg was performed using TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The direct ground-state to ground-state atomic mass difference between $^{22}$Mg and $^{22}$Na was determined to be $Q_{EC}=4781.40(22)$~keV, representing the most precise single measurement of this quantity to date. In a continued push towards calculating superallowed isospin-symmetry-breaking (ISB) corrections from first principles, ab-initio shell-model calculations of the $A=22$ IMME are also presented for the first time using the valence-space in-medium similarity renormalization group formalism. With particular starting two- and three-nucleon forces, this approach demonstrates a level of agreement with the experimental data that suggests reliable ab-initio calculations of superallowed ISB corrections are now possible.