Superallowed 0+→0+ nuclear β-decays: A critical survey with tests of CVC and the standard model

A complete and critical survey is presented of all lifetime, decay-energy and branching-ratio measurements relating to the superallowed 0+→0+ decays of 14O, 26mAl, 34Cl, 38mK, 42Sc, 46V, 50Mn and 54Co; no measurements are ignored, though some are rejected and others are updated. The associated calculations and theoretical corrections needed to convert these results into Ft values are also described and critically assessed. The resulting Ft values are then presented with careful attention to the origin and magnitude of their uncertainties. As an exacting confirmation of the conserved-vector-current hypothesis, the Ft values are seen to be constant to 4 parts in 104. In addition, the effective vector coupling constant of nuclear β decay is determined to be G'v/(ℎc)3 = (1.14939±0.00065)x10-5 GeV-2; the up-down quark-mixing element of the Kobayashi-Maskawa matrix is Vud=0.9740±0.0010; and the unitary test on the top row of the matrix becomes vertical strokeVudvertical stroke2+vertical strokeVusvertical stroke2+vertical strokeVubvertical stroke2 = 0.9970±0.0021, which sets a useful limit on the possible participation of a fourth generation of quarks. The data are also used to set a new limit for the Fierz interference term, bF≤0.004, and for possible mixing of massive neutrinos. Finally, the results are shown to be consistent with, though more precise than, the current data for neutron and pion decay. (orig.)