Measurement of the Branching Ratio for the Beta Decay of $^{14}$O

TL;DR

This paper reports a precise measurement of the branching ratio for $^{14}$O beta decay to the ground state of $^{14}$N, refining the partial half-life and impacting the determination of the CKM matrix element $V_{ud}$.

Contribution

The study provides a more accurate measurement of the $^{14}$O decay branching ratio, improving the precision of superallowed Fermi decay parameters and CKM matrix tests.

Findings

Branching ratio significantly smaller than previous measurements

Improved partial half-life for superallowed decay

Enhanced agreement of ${ m Ft}$ value with other superallowed decays

Abstract

We present a new measurement of the branching ratio for the decay of $^{14}$O to the ground state of $^{14}$N. The experimental result, $\lambda _0/\lambda _{\rm total} = (4.934 \pm 0.040\kern 1pt{\rm (stat.)} \pm 0.061\kern 1pt{\rm (syst.)}) \times 10^{-3}$, is significantly smaller than previous determinations of this quantity. The new measurement allows an improved determination of the partial halflife for the superallowed $0^+ \rightarrow 0^+$ Fermi decay to the $^{14}$N first excited state, which impacts the determination of the $V_{ud}$ element of the CKM matrix. With the new measurement in place, the corrected $^{14}$O ${\cal F} t $ value is in good agreement with the average ${\cal F} t $ for other superallowed $0^+ \rightarrow 0^+$ Fermi decays.