Semileptonic hyperon decays and Cabibbo-Kobayashi-Maskawa unitarity

Using a technique that is not subject to first-order SU(3) symmetry breaking effects, we determine the V-us element of the Cabibbo-Kobayashi-Maskawa matrix from data on semileptonic hyperon decays. We obtain V-us=0.2250(27), where the quoted uncertainty is purely experimental. This value is of similar experimental precision to the one derived from K-l3, but it is higher and thus in better agreement with the unitarity requirement, \V-ud\(2)+\V-us\(2)+\V-ub\(2)=1. An overall fit, including the axial contributions and neglecting SU(3) breaking corrections, yields F+D=1.2670 +/-0.0035 and F-D=-0.341+/-0.016 with chi(2)=2.96/3 degrees of freedom.