Semi-leptonic decays on the lattice: The exclusive 0- to 0- case

We present our results for the meson form factors of several semi- leptonic decays. They are computed from the corresponding matrix elements evaluated on the lattice as ratios of Greens functions. The renormalization of the local operators is calculated nonperturbatively. The dependence of the form factors on the four momentum transfer q2 is studied by injecting external three momenta to the initial and final state mesons. We study the pseudoscalar decays K → π ell ν, D → K ell ν, D → π ell ν, Ds → η ell ν and Ds → K ell ν on different lattices. We also analyze scaling, finite size and SU(3) symmetry breaking effects. The uncertainties in some lattice parameters, e.g. a-1, as a source of systematic errors in this calculation are discussed. 35 refs., 15 figs., 13 tabs