The decay constants of B, D and K mesons are computed in quenched lattice QCD at two different values of the coupling. The action and operators are O(a) improved with non-perturbative coefficients. The results are f B = 195(6) +24 −23 MeV, f D = 206(4) +17 −10 MeV, f Bs = 220(6) +23 −28 MeV, f Ds = 229(3) +23 −12 MeV and f K = 150(3) +12 − 8MeV. Systematic errors are discussed in detail. Results for vector decay constants, flavour symmetry breaking ratios of decay constants, the pseudoscalar-vector mass splitting and D meson masses are also presented.

We present results of a lattice analysis of the B parameter B B , the decay constant f B , and several mass splittings using the static approximation. Results were obtained for 60 quenched gauge configurations computed at ␤ϭ6.2 on a lattice size of 24 3 ϫ48. Light quark propagators were calculated using the O(a)-improved Sheikholeslami-Wohlert action. We findcorresponding to B B static ϭ1.02 Ϫ6 Ϫ2 ϩ5 ϩ3 , f B static ϭ266 Ϫ20 Ϫ27 ϩ18 ϩ28 MeV, and f B s 2 B B s / f B 2 B B ϭ1.34 Ϫ8 Ϫ3 ϩ9 ϩ5 , where a variational fitting technique was used to extract f B static . For the mass splittings we obtain M B s ϪM B d ϭ87 Ϫ12 Ϫ12 ϩ15 ϩ6 MeV, M ⌳ b ϪM B d ϭ420 Ϫ90 Ϫ30 ϩ100 ϩ30 MeV, and M B* 2 ϪM B 2 ϭ0.281 Ϫ16 Ϫ37 ϩ15 ϩ40 GeV 2 . We compare different smearing techniques in-tended to improve the signal/noise ratio. From a detailed assessment of systematic effects, we conclude that the main systematic uncertainties are associated with the renormalization constants relating a lattice matrix element to its continuum counterpart. The dependence of our findings on lattice artifacts is to be investigated in the future. ͓S0556-2821͑96͒04715-7͔

We present results from quenched lattice QCD for the form factors for the decay B → ρlν. The calculations are performed using a nonperturbatively improved action and operators at two values of the lattice spacing. The bottom quark mass is reached by extrapolation from simulations performed with heavy quark masses around the charm mass. Our primary result is for the partially integrated decay rate Γ PI over the range 12.7 GeV 2 < q 2 < 18.2 GeV 2 :Γ PI = 4.9 +12 −10 + 0 −14 × 10 12 s −1 |V ub | 2 .