| Q Value of the Superallowed Decay of $^{46}$V and Its Influence on $V_ud$ and the Unitarity of the Cabibbo-Kobayashi-Maskawa Matrix (2005) | |||||||||||||||
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Abstract | |||||||||||||||
| The masses of the radioactive nuclei $^{46}$V and its decay daughter $^{46}$Ti have been measured with the Canadian Penning Trap on-line Penning trap mass spectrometer to a precision of 1$\times10^{-8}$. A QEC value of 7052.90(40) keV for the superallowed beta decay of $^{46}$V is obtained from the difference of these two masses. With this precise Q value, the [script F]t value for this decay is determined with improved precision. An investigation of an earlier Q-value measurement for $^{46}$V uncovers a set of 7 measurements that cannot be reconciled with modern data and affects previous evaluations of V$_{ud}$ from superallowed Fermi decays. A new evaluation, adding our new data and removing the discredited subset, yields new values for G$_V$ and V$_{ud}$. When combined with recent results for V$_{us}$, this yields modified constraints for the unitarity of the Cabibbo-Kobayashi-Maskawa matrix and other extensions of the standard model. | |||||||||||||||
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