Precise half-life determination of the mixed-mirror beta-decaying O-15

The half-life of O-15 was measured using the beta-Counting Station at the University of Notre Dame's Nuclear Science Laboratory. Our new result, t(1/2) = 122.308(49) s, is the most precise determination to date for O-15, and improves the world average by a factor of 4, yielding t(1/2)(world) 122.27(6) s. This more precise value will be important for future determinations of V-ud using superallowed T = 1/2 mirror transitions.