Precise Half-Life Measurement of $^{46}$V

The $^{46}$V is one of the key superallowed transitions contributing to precision tests of the conserved vector current hypothesis and the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. Recent Penning-trap $Q_{EC}$ measurements of the superallowed $\beta$ decay of $^{46}$V showed an earlier reaction-based result to be wrong and raised the $Ft$ value by nearly three standard deviations from the average of all other well-known superallowed transitions. This anomaly raised the possibility of systematic effects for all reaction-based $Q$- value measurements and led to a theoretical reexamination of the isospin-symmetry-breaking corrections for superallowed decays. The improved corrections removed the anomalous result of $^{46}$V and restored agreement among the corrected $Ft$ values. Throughout these changes, the previously accepted half- life of $^{46}$V was assumed to be completely correct. We have now tested this assumption by measuring a new precise half-life of $^{46}$V. The preliminary result, 422.67(10) ms, agrees with but is more precise than previous values.