Semileptonic B Decays with Nf=2+1 Dynamical Quarks

Semileptonic, B → π l ν ¯ , decays are studied on the MILC dynamical configuration using NRQCD heavy and Asqtad light quarks. We work with light valence quark masses ranging between m s and m s / 8 . Preliminary simple linear chiral extrapolations have been carried out for form factors f ‖ and f ⊥ at fixed E π . The chirally extrapolated results for the form factors f + ( q 2 ) and f 0 ( q 2 ) are then fit to the Becirevic–Kaidalov (BK) ansatz. Preliminary estimates of the CKM matrix element | V u b | are presented on recently published branching fractions for B 0 → π − l + ν exclusive decays by the CLEO collaboration.