Quenched lattice calculation of the B -> Dlv decay rate

We calculate, in the continuum limit of quenched lattice QCD, the form factor that enters in the decay rate of the semileptonic decay B -> Dlv. Making use of the step scaling method (SSM), previously introduced to handle two scale problems in lattice QCD, and of flavour twisted boundary conditions we extract G(B -> D)(w) at finite momentum transfer and at the physical values of the heavy quark masses. Our results can be used in order to extract the CKM matrix element V-cb by the experimental decay rate without model dependent extrapolations. (c) 2007 Elsevier B.V. All rights reserved