Ft value of the 0+→0+ β+ decay of Ar32: A measurement of isospin symmetry breaking in a superallowed decay

We determined the absolute branch of the T=2 superallowed decay of Ar32 by detecting the β+-delayed protons and γ decays of the daughter state. We obtain bSAβ=(22.71±0.16)%, which represents the first determination of a proton branch to better than 1%. Using this branch along with the previously determined Ar32 half-life and energy release, we determined ft=(1552±12) s for the superallowed decay. This ft value, together with the corrected Ft value extracted from previously known T=1 superallowed decays, yields a measurement of the isospin symmetry breaking correction in Ar32 decay δCexp=(2.1±0.8)%. This can be compared to a theoretical calculation δC=(2.0±0.4)%. As by-products of this work, we determined the γ and proton branches for the decay of the lowest T=2 state of Cl32, made a precise determination of the total proton branch and relative intensities of proton groups that leave S31 in its first excited state and deduced an improved value for the Cl32 mass. © 2008 The American Physical Society.