SU(3)-breaking corrections to the hyperon vector coupling f1(0) in covariant baryon chiral perturbation theory

We report on a recent study of the SU(3)-breaking corrections to the hyperon vector coupling f1(0) up to O(p4) in covariant baryon chiral perturbation theory with dynamical octet and decuplet contributions. The decuplet contributions are taken into account for the first time in a covariant ChPT study and are found of similar or even larger size than the octet ones. We predict positive SU(3)-breaking corrections to all the four independent f1(0)’s (assuming isospin symmetry), which are consistent, within uncertainties, with the latest results from large Nc fits, chiral quark models, and quenched lattice QCD calculations. We also discuss briefly the implications of our results for the extraction of Vus from hyperon decay data.