We calculate the form factors for the semileptonic decays $B_sto Kell u$ and $Bto Kellell$ with lattice QCD. We work at several lattice spacings and a range of light quark masses, using the MILC 2+1-flavor asqtad ensembles. We use the Fermilab method
for the $b$ quark. We obtain chiral-continuum extrapolations for $E_K$ up to $sim1.2$ GeV and then extend to the entire kinematic range with the model-independent $z$ expansion.
We report on form factors for the B->K l^+ l^- semi-leptonic decay process. We use several lattice spacings from a=0.12 fm down to 0.06 fm and a variety of dynamical quark masses with 2+1 flavors of asqtad quarks provided by the MILC Collaboration. T
hese ensembles allow good control of the chiral and continuum extrapolations. The b-quark is treated as a clover quark with the Fermilab interpretation. We update our results for f_parallel and f_perp, or, equivalently, f_+ and f_0. In addition, we present new results for the tensor form factor f_T. Model independent results are obtained based upon the z-expansion.
