Measurement of the Branching Ratio for the Beta Decay of ¹⁴O

We present a new measurement of the branching ratio for the decay of 14O to the ground state of 14N. The experimental result, l0/ltotal = (4.934 0.040(stat.) 0.061(syst.)) ×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+ 0+ Fermi decay to the 14N first excited state, which impacts the determination of the Vud element of the CKM matrix. With the new measurement in place, the corrected 14O F t value is in good agreement with the average F t for other superallowed 0+ 0+ Fermi decays.