B-MESON AND D-MESON DECAY CONSTANTS IN LATTICE QCD - ART. NO. 014506

We have calculated the decay constants of B and D mesons with lattice QCD. We use an O(a)-improved action that takes light quark actions as a starting point, tuned so that it can be directly applied at the phys ical masses of the b and c quarks. Our results are f(B)=164(-11)(+14)/-8 MeV, f(Bs)=185(-8)(+13)+/-9 MeV, f(D)=194(-10)(+14) +/-10 MeV, and f(Ds)=213(-11)(+14)+/-11 MeV in the quenched approximation. The first error in each case is statistical, and the second is from perturbatio n theory. We show that discretization errors are under control in our approach and smaller than our statistical errors. The effects of the q uenched approximation may raise our quenched result by up to 10%. [S05 56-2821(98)07013-1].