Precision half-life measurement of the beta(+) decay of K-37
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2014 American Physical Society. The half-life of K37 has been measured to be 1.23651(94)s, a value nearly an order of magnitude more precise than the best previously reported. The + decay of K37 occurs mainly via a superallowed branch to the ground state of its T=1/2 mirror, Ar37. This transition has been used recently, together with similar transitions from four other nuclei, as a method for determining Vud, but the precision of its ft value was limited by the relatively large half-life uncertainty. Our result corrects that situation. Another motivation for improving the ft value was to determine the standard-model prediction for the -decay correlation parameters, which will be compared to those currently being measured by the TRINAT Collaboration at TRIUMF. The new ft value, 4605(8)s, is now limited in precision by the 97.99(14)% ground-state branching ratio.