Determination of the Kobayashi-Maskawa-Cabibbo matrix element Vus under various flavor-symmetry-breaking models in hyperon semileptonic decays.

We study the success to describe hyperon semileptonic decays of four models that incorporate second-order SU(3) symmetry breaking corrections. The criteria to assess their success is by determining Vus in each of the three relevant hyperon semileptonic decays and comparing the values obtained with one another and also with the one that comes from Kl3 decays. A strong dependence on the particular symmetry breaking model is observed. Values of Vus which do not agree with the one of Kl3 are generally obtained. However, in the context of chiral perturbation theory, only the model whose corrections are O(ms) and O(m 3/2 s ) is successful. Using its predictions for the f1 form factors one can quote a value of Vus from this model, namely, Vus = 0.2176± 0.0026, which is in excellent agreement with the Kl3 one. PACS Numbers: 13.30.Ce, 12.15.Hh, 12.15.Ji Typeset using REVTEX