Computation of the heavy-light decay constant using nonrelativistic lattice QCD.

We report results on a lattice calculation of the heavy-light meson decay constant employing the non-relativistic QCD approach for heavy quark and Wilson action for light quark. Simulations are carried out at β = 6.0 on a 16 × 48 lattice. Signal to noise ratio for the ground state is significantly improved compared to simulations in the static approximation, enabling us to extract the decay constant reliably. We compute the heavy-light decay constant for several values of heavy quark mass and estimate the magnitude of the deviation from the heavy mass scaling law fP √ mP = const. For the B meson we find fB = 171±22 −45 MeV, while an extrapolation to the static limit yields f static B = 297± 36 −30 MeV.