Computation of the Heavy-Light Decay Constant with NRQCD

Non-relativistic QCD is applied for a lattice computation of the heavy-light meson decay constant in quenched approximation at $\beta =6.0$. Clear signals are obtained for the ground state at large times in the correlators, allowing a reliable extraction of the decay constant. Estimating the current renormalization factor by the tadpole improvement procedure, we find $f_B=$ 164(17) MeV for the $B$ meson with $a^{-1}=$ 2.3 GeV, while an extrapolation to the static limit yields $f_B^{static}=$ 247(26) MeV.