Vus Determination from Hyperon Semileptonic Decays

We analyze the numerical determination of the quark mixing factor Vus from hyperon semileptonic decays. The discrepancies between the results obtained in two previous studies are clarified. Our fits indicate sizeable SU(3) breaking corrections, which unfortunately can only be fully determined from the data at the first order. The lack of a reliable theoretical calculation of second-order symmetry breaking effects translates into a large systematic uncertainty, which has not been taken into account previously. Our final result, |Vus| = 0.226 ± 0.005, is not competitive with the existing determinations from Kl3, Kl2 and τ decays.