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

• Received 11 August 2015

DOI:https://doi.org/10.1103/PhysRevC.92.065502