DETERMINATION OF VERTICAL-BAR-V(UD)VERTICAL-BAR FROM FERMI DECAYS AND THE UNITARITY OF THE KM-MIXING MATRIX

We re-evaluate the ft-values and their radiative corrections for the eight superallowed beta+ decays for which very accurate data are available and also include the results for C-10, for which the measurements are approaching a similar accuracy. The main new feature is a recalculation of the nuclear-structure dependent part C(NS) of the O(alpha) radiative correction using wave functions more realistic than those used previously. This determines the value of the element V(ud) of the quark mixing matrix. Moreover, we recalculate V(us) in the framework of a quark model. The resulting values of these two matrix elements indicate a violation of unitarity of the mixing matrix. We discuss implications of this regarding possible extensions of the minimal version of the standard model of electroweak interactions.