B → πlν Semileptonic Decays from Lattice QCD using Highly Improved Staggered Quarks

We present preliminary lattice QCD calculations of the semileptonic decay for B→ πlν . Our calculation uses the highly improved staggered quark (HISQ) action for all valence and sea quarks and includes Nf = 2+1+1 MILC ensembles with lattice spacings ranging from a≈0.12 fm down to 0.03 fm. The HISQ action allows all the quarks to be treated with the same relativistic light-quark action, allowing for nonperturbative renormalization using partial conservation of the vector current. We plan to combine our results with experimental measurements of the differential decay rate to determine Vub.