Improved B ->pi l nu(iota) form factors from the lattice

We present the results of a lattice computation of the form factors for B-0 --> pi(-)l(+)nu(l) decays near zero-recoil. These results will allow a det ermination of the CKM matrix element \V-ub\ when measurements of the differ ential decay rate become available. We also provide models for extrapolatio n of the form factors and rate to the full recoil range. Our computation is performed in the quenched approximation to QCD on a 24(3) x 48 lattice at beta = 6.2, using a non-perturbatively O(a)-improved action. The masses of all light valence quarks involved are extrapolated to their physical values . (C) 2000 Elsevier Science B.V. All rights reserved.