Bs → Klν form factors from lattice QCD

We report the first lattice QCD calculation of the form factors for the standard model tree-level decay B-s -> Kl nu. In combination with future measurement, this calculation will provide an alternative exclusive semileptonic determination of vertical bar V-ub vertical bar. We compare our results with previous model calculations, make predictions for differential decay rates and branching fractions, and predict the ratio of differential branching fractions between B-s -> K tau nu and B-s -> K mu nu. We also present standard model predictions for differential decay rate forward- backward asymmetries and polarization fractions and calculate potentially useful ratios of B-s -> K form factors with those of the fictitious B-s -> eta(s) decay. Our lattice simulations utilize nonrelativistic QCD b and highly improved staggered light quarks on a subset of the MILC Collaboration 2 + 1 asqtad gauge configurations, including two lattice spacings and a range of light quark masses.