arXiv subjects
Publications and source records attributed to R. Flores-Mendieta.
We review the recent experimental and theoretical progress in the determination of |V_{ud}| and |V_{us}|, and the status of the most stringent test of CKM unitarity. Future prospects on |V_{cd}| and |V_{cs}| are also briefly discussed.
We obtain a model-independent expression for the Dalitz plot of semileptonic decays of polarized hyperons including radiative corrections to order alpha and neglecting terms of order (alpha q)/(pi M_1), where q is the four-momentum transfer and M_1 is the mass of the decaying hyperon. We specialize our results to exhibit the correlation between the charged-lepton momentum and the spin of the decaying hyperon. We present results for the three-body region of the Dalitz plot and for the complete Dalitz plot (which includes the four-body region). From these results we also obtain the corresponding radiative corrections to the integrated lepton spin-asymmetry coefficient. Our formulas are valid for charged as well as for neutral decaying hyperons and are appropriate for model-independent experimental analysis whether the real photon is discriminated or not.
Tree amplitudes for baryon-pion scattering are studied in the 1/N_c expansion. Generalized large-N_c consistency conditions are obtained to all orders in baryon mass splittings. For baryons with spin J ~ O(1), the leading order in N_c tree amplitudes can be evaluated keeping only terms up to a given finite order in baryon mass splittings.
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.