Bmeson semileptonic form factors from unquenched lattice QCD

The semileptonic process, B→πlν, is studied via full QCD lattice simulations. We use unquenched gauge configurations generated by the MILC Collaboration. These include the effect of vacuum polarization from three quark flavors: the s quark and two very light flavors ($u/d$) of variable mass allowing extrapolations to the physical chiral limit. We employ nonrelativistic QCD to simulate the b quark and a highly improved staggered quark action for the light sea and valence quarks. We calculate the form factors f₊(q²) and f₀(q²) in the chiral limit for the range 16 GeV²≤q²<qmax² and obtain ∫_16 GeV²^qmax²[dΓ/dq²]dq²/|Vub|²=1.46(35) ps^-1. Combining this with a preliminary average by the Heavy Flavor Averaging Group (HFAG'05) of recent branching fraction data for exclusive B semileptonic decays from the BABAR, Belle and CLEO Collaborations leads to |Vub|=4.22(30)(51)×10^-3.