A detailed study of orbital and radial excited states in D,D s ,B, and B s systems is performed. The chiral quark model provides the framework for the calculation of pseudoscalar meson (,K, . . . ) hadronic transitions among heavy-light excited and ground states. To calculate the excited states masses and wave functions, we must resort to a relativistic quark model. Our model includes the leading order corrections in 1/m (c,b) ͑e.g., mixing͒. Numerical results for masses and light hadronic transition rates are compared to existing experimental data. The effective coupling of the chiral quark model can be determined by comparing with independent results from lattice simulations (g A 8 ϭ0.53Ϯ0.11) or fitting to known widths (g A 8 ϭ0.82Ϯ0.09).
The recently developed Symanzik-improved staggered-quark discretization allows unquenched lattice-QCD simulations with much smaller (and more realistic) quark masses than previously possible. To test this formalism, we compare experiment with a variety of nonperturbative calculations in QCD drawn from a restricted set of "gold-plated" quantities. We find agreement to within statistical and systematic errors of 3% or less. We discuss the implications for phenomenology and, in particular, for heavy-quark physics.
We calculate the leptonic decay constants of B (s) and D (s) mesons in lattice QCD using staggered light quarks and Fermilab bottom and charm quarks. We compute the heavy-light meson correlation functions on the MILC asqtad-improved staggered gauge configurations which include the effects of three light dynamical sea quarks. We simulate with several values of the light valence-and seaquark masses (down to ∼ ms/10) and at three lattice spacings (a ≈ 0.15, 0.12, and 0.09 fm) and extrapolate to the physical up and down quark masses and the continuum using expressions derived in heavy-light meson staggered chiral perturbation theory. We renormalize the heavy-light axial current using a mostly nonperturbative method such that only a small correction to unity must be computed in lattice perturbation theory and higher-order terms are expected to be small. We use the two finer lattice spacings for our central analysis and use the third to help estimate discretization errors. We obtain f B + = 196.9(9.1) MeV, fB s = 242.0(10.0) MeV, f D + = 218.9(11.3) MeV, fD s = 260.1(10.8) MeV, and the SU(3) flavor-breaking ratios fB s /fB = 1.229(26) and fD s /fD = 1.188(25), where the numbers in parentheses are the total statistical and systematic uncertainties added in quadrature.
We calculate the form factor f + (q 2 ) for B-meson semileptonic decay in unquenched lattice QCD with 2+1 flavors of light sea quarks. We use Asqtad-improved staggered light quarks and a Fermilab bottom quark on gauge configurations generated by the MILC Collaboration. We simulate with several light quark masses and at two lattice spacings, and extrapolate to the physical quark mass and continuum limit using heavy-light meson staggered chiral perturbation theory. We then fit the lattice result for f + (q 2 ) simultaneously with that measured by the BABAR experiment using a parameterization of the form factor shape in q 2 which relies only on analyticity and unitarity in order to determine the CKM matrix element |V ub |. This approach reduces the total uncertainty in |V ub | by combining the lattice and experimental information in an optimal, model-independent manner. We find a value of |V ub | × 10 3 = 3.38 ± 0.36.
We present the first lattice QCD calculation with realistic sea quark content of the D+-meson decay constant f(D+). We use the MILC Collaboration's publicly available ensembles of lattice gauge fields, which have a quark sea with two flavors (up and down) much lighter than a third (strange). We obtain f(D+)=201+/-3+/-17 MeV, where the errors are statistical and a combination of systematic errors. We also obtain f(Ds)=249+/-3+/-16 MeV for the Ds meson.
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