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Mark Galassi Los Alamos National Laboratory Jim Davies Department of Computer Science, Georgia Institute of Technology James Theiler Astrophysics and Radiation Measurements Group, Los Alamos National Laboratory Brian Gough Network Theory Limited Gerard Jungman Theoretical Astrophysics Group, Los Alamos National Laboratory Patrick Alken Department of Physics, University of Colorado at Boulder Michael Booth Department of Physics and Astronomy, The Johns Hopkins University Fabrice Rossi University of Paris-Dauphine

We present a study of the effects of improvement on light-quark physics using the Fermilab formalism. The calculations were performed at three different lattice spacings, with the SW action and traditional Wilson action (both tadpole improved). We find that O(a) effects for the decay constant f(pi) and quark mass m(q) can be successfully removed using the tadpole-improved SW action in the light-quark regime.

We present a study of the effects of improvement on light-quark physics using the Fermilab formalism. The calculations were performed at three different lattice spacings, with the SW action and traditional Wilson action (both tadpole improved). We find that O(a) effects for the decay constant fπ and quark mass mq can be successfully removed using the tadpole-improved SW action in the light-quark regime.

We present results of a lattice computation of the vector and axial-vector current matrix elements relevant for the semileptonic decay B^0-bar -> rho^+ l^- nu_l-bar. The computations are performed in the quenched approximation of lattice QCD on a 24^3 x 48 lattice at beta = 6.2, using an O(a) improved fermionic action. Our principal result is for the differential decay rate, dGamma/dq^2, for the decay B^0-bar -> rho^+ l^- nu_l-bar in a region beyond the charm threshold, allowing a model-independent extraction of |V_{ub}| from experimental measurements. Heavy quark symmetry relations between radiative and semileptonic decays of B-bar mesons into light vector mesons are also discussed.

We present updated results on the calculation of the matrix elements for B --> K'gamma in the quenched approximation on a 24(3) x 48 lattice at beta=6.2, using an O(alpha)-improved fermion action. The scaling behaviours of the form factors T-1 (q(2)=0) and T-2(q(max)(2)) for the decay are examined and pole model ansatzes tested.