Precise half-life measurement for the superallowed 0+ → 0+ β emitter 74Rb:: First results from the new radioactive beam facility (ISAC) at TRIUMF

Presently, the world data fur superallowed beta decay leads to a result in disagreement (at the 98% confidence level) with the predictions of the minimal standard model fur the unitarity of the Cabibbo-Kubayashi-Maskawa matrix. Precise data for the superallowed 0(+) --> 0(+) beta decay of Rb-74 would provide a critical test of the: nucleus-dependent isospin symmetry-breaking corrections that must be calculated for these: superallowed Fermi beta decays. The present work reports the first precise measurement of the half-life for Rb-74 (t(1/2) = 64.761 +/- 0.031 ms). The data were obtained at the radioactive beam facility (ISAC) at TRIUMF using a beam of similar to 4000 Rb-74 ions s(-1).