Nonperturbatively improved heavy-light mesons: Masses and decay constants

We present a study of the heavy-light spectrum and of the D- and B-meson decay constants. The results were obtained in the quenched approximation, by using the nonperturbatively improved clover lattice action at beta =6.2, with a sample of 100 configurations, on a 24(3)x64 lattice. After a careful analysis of the systematic errors present in the extraction of the physical results, by assuming quite conservative discretization errors, we find f(D)=231+/-12(-1)(+8) Mev, f(D) = 211 +/- 14(-12)(+2), MeV f(Ds)/f(D) = 1.10(2) f(Bs) = 204+/-16(-0)(+36) MeV, f(B)=179 +/-18(-9)(+34) MeV, f(Bs)/f(B) = 1.14(3)(-1)(+1). Our results, which have smaller discretization errors than many previous estimates at fixed value of the lattice spacing a, support a large value of f(B) in the quenched approximation. [S0556-2821(99)00317-3].