Semileptonic B Decays from an NRQCD/D234 Action

Semileptonic B decays are studied on quenched anisotropic lattices using Symanzik improved glue, NRQCD heavy quark and D234 light quark actions. We employ constrained fits to extract ground state contributions to two- and three-point correlators. Results for the B --> pi, l nubar decay form factors are compared with previous lattice results. We find that our systematic errors (excluding quenching errors) are dominated by chiral extrapolation uncertainties.Comment: Lattice2002(Heavy quark physics

B Physics with NRQCD: A Quenched Study

We present results on the spectrum of B mesons and heavy baryons, using a non-relativistic formulation for the heavy and a clover action for the light quark. We also discuss B meson decay constants and their dependency upon the heavy meson mass.Comment: 4 pages, uuencoded compressed postscript file, contribution to LATTICE 9

Dynamical determination of B_K from improved staggered quarks

The scaling corrections that affected previous staggered calculations of B_K have been proved to be reduced by using improved actions (HYP, Asqtad) in the quenched approximation. This improved behaviour allows us to perform a reliable dynamical calculation of B_K including quark vacuum polarization effects using the MILC (2+1) flavour dynamical configurations. We report here on the results from such dynamical calculation. We also discuss the renormalization effects with the Asqtad action.Comment: 6 pages, 2 figures. Talk presented at Lattice 2005 (Dublin). To appear in Proceedings of Scienc

F_B from moving B mesons

We show results for the B meson decay constant calculated both for B mesons at rest and those with non-zero momentum and using both the temporal and spatial components of the axial vector current. It is an important check of lattice systematic errors that all these determinations of f_B should agree. We also describe how well different smearings for the B meson work at non-zero momentum - the optimal smearing has a narrow smearing for the b quark.Comment: Lattice2001(heavyquark

Scaling and Further Tests of Heavy Meson Decay Constant Determinations from Nonrelativistic QCD

We present results for the B_s meson decay constant f_{B_s} from simulations at three lattice spacings in the range a^{-1}=1.1 to 2.6 GeV using NRQCD heavy quarks and clover light quarks in the quenched approximation. We study scaling of this quantity and check the consistency between mesons decaying from rest and from a state with nonzero spatial momentum. The cancellation of power law contributions that arise in the NRQCD formulation of heavy-light currents is discussed. On the coarsest lattice the D_s meson decay constant f_{D_s} is calculated. Our best values for the decay constants are given by f_{B_s} = 187(4)(4)(11)(2)(7)(6) MeV and f_{D_s} = 223(6)(31)(38)(23)(9)(^{+3}_{-1}) MeV.Comment: 29 pages with 7 postscript figures, improved error analysis, version to appear in Physical Review

D→K,lνD \rightarrow K, l \nu Semileptonic Decay Scalar Form Factor and ∣Vcs∣|V_{cs}| from Lattice QCD

We present a new study of D semileptonic decays on the lattice which employs the Highly Improved Staggered Quark (HISQ) action for both the charm and the light valence quarks. We work with MILC unquenched $N_f = 2 + 1$ lattices and determine the scalar form factor $f_0(q^2)$ for $D \rightarrow K, l \nu$ semileptonic decays. The form factor is obtained from a scalar current matrix element that does not require any operator matching. We develop a new approach to carrying out chiral/continuum extrapolations of $f_0(q^2)$. The method uses the kinematic "$z$" variable instead of $q^2$ or the kaon energy $E_K$ and is applicable over the entire physical $q^2$ range. We find $f^{D \rightarrow K}_0(0) \equiv f^{D \rightarrow K}_+(0) = 0.747(19)$ in the chiral plus continuum limit and hereby improve the theory error on this quantity by a factor of $\sim$4 compared to previous lattice determinations. Combining the new theory result with recent experimental measurements of the product $f^{D \rightarrow K}_+(0) * |V_{cs}|$ from BaBar and CLEO-c leads to the most precise direct determination of the CKM matrix element $|V_{cs}|$ to date, $|V_{cs}| = 0.961(11)(24)$, where the first error comes from experiment and the second is the lattice QCD theory error. We calculate the ratio $f^{D \rightarrow K}_+(0)/f_{D_s}$ and find $2.986 \pm 0.087$ GeV$^{-1}$ and show that this agrees with experiment.Comment: 23 pages, 31 figures, 11 tables. Added a paragraph in sction VII, and updated with PDG 2010 instead of PDG 200