Precision half-life measurement of the \boldmath$\beta^+$ decay of \tsups{37}K

TL;DR

This paper reports a highly precise measurement of the half-life of sups{37}K, significantly improving the accuracy of its $ft$ value, which is crucial for testing the Standard Model and understanding weak interactions.

Contribution

The study provides the most precise half-life measurement of sups{37}K, refining the $ft$ value used in fundamental tests of the weak interaction and nuclear structure.

Findings

Half-life of sups{37}K measured as 1.23651(94) s

New $ft$ value of 4605(8) s with improved precision

Results enhance tests of CVC and Standard Model predictions

Abstract

The half-life of \tsups{37}K has been measured to be $1.23651(94)~\mathrm{s}$, a value nearly an order of magnitude more precise than the best previously reported. The $\beta^+$ decay of \tsups{37}K occurs mainly via a superallowed branch to the ground-state of its $T=1/2$ mirror, \tsups{37}Ar. This transition has been used recently, together with similar transitions from four other nuclei, as an alternative test of CVC and method for determining $V_{ud}$, but the precision of its $ft$ value was limited by the relatively large half-life uncertainty. Our result corrects that situation. Another motivation for improving the $ft$ value was to determine the standard-model prediction for the $\beta$-decay correlation parameters, which will be compared to those currently being measured by the \trinat{} collaboration at \triumf. The new $ft$ value, $4605(8)~\mathrm{s}$, is now limited in precision by the $97.99(14)\%$ ground-state branching ratio.