Semileptonic form factors D →π, K and B →π, K from a fine lattice

Abstract

We extract the form factors relevant for semileptonic decays of D and B mesons from a relativistic computation on a fine lattice in the quenched approximation. The lattice spacing is a=0.04 fm (corresponding to a^=4.97 GeV), which allows us to run very close to the physical B meson mass, and to reduce the systematic errors associated with the extrapolation in terms of a heavy quark expansion. For decays of D and D_s mesons, our results for the physical form factors at q^2=0 are as follows: f_+^(0)= 0.74(6)(4), f_+^(0)= 0.78(5)(4) and f_+^(0)=0.68(4)(3). Similarly, for B and B_s we find: f_+^(0)=0.27(7)(5), f_+^(0)=0.32(6)(6) and f_+^(0)=0.23(5)(4). We compare our results with other quenched and unquenched lattice calculations, as well as with light-cone sum rule predictions, finding good agreement.