Determination of the Kobayashi-Maskawa-Cabibbo matrix element V_{us}   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 V_{us} 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 K_{l3} decays. A strong dependence on the particular symmetry breaking model is observed. Values of V_{us} which do not agree with the one of K_{l3} are generally obtained. However, in the context of chiral perturbation theory, only the model whose corrections are O(m_s) and O(m_s^{3/2}) is successful. Using its predictions for the f_1 form factors one can quote a value of V_{us} from this model, namely, V_{us}=0.2176\pm 0.0026, which is in excellent agreement with the K_{l3} one. 
R. Flores-Mendieta (1), A. Garcia (1), and G. Sanchez-Colon (2) ((1)   CINVESTAV-DF, (2) CINVESTAV-Merida)