First lattice QCD study of the image axial and vector form factors with image breaking corrections Original Research Article

We present the first quenched lattice QCD study of the form factors relevant for the hyperon semileptonic decay image. The momentum dependence of both axial and vector form factors is investigated and the values of all the form factors at zero-momentum transfer are presented. Following the same strategy already applied to the decay image, the image-breaking corrections to the vector form factor at zero-momentum transfer, image, are determined with great statistical accuracy in the regime of the simulated quark masses, which correspond to pion masses above image. Besides image also the axial to vector ratio image, which is relevant for the extraction of the CKM matrix element image, is determined with significant accuracy. Due to the heavy masses involved, a polynomial extrapolation, which does not include the effects of meson loops, is performed down to the physical quark masses, obtaining image and image, where the uncertainties do not include the quenching effect. Adding a recent next-to-leading order determination of chiral loops, calculated within the Heavy Baryon Chiral Perturbation Theory in the approximation of neglecting the decuplet contribution, we obtain image. Our findings indicate that image-breaking corrections are moderate on both image and image. They also favor the experimental scenario in which the weak electricity form factor, image, is large and positive, and correspondingly the value of image is reduced with respect to the one obtained with the conventional assumption image based on exact image symmetry.