367 research outputs found

    Parametrisations of the D -> K l nu form factor and the determination of \hat{g}

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    The vector form factor f_+(t) of the semileptonic decay D -> K l nu, measured recently with a high accuracy, can be used to determine the strong coupling constant g_{D_s^* D K}. The latter is related to the normalised coupling \hat{g} releveant in heavy-meson chiral perturbation theory. This determination relies on the estimation of the residue of the form factor at the D_s^* pole and thus on an extrapolation of the form factor in the unphysical region (m_D-m_K)^2<t<(m_D+m_K)^2. We test this extrapolation for several parametrisations of the form factors by determining the value of \hat{g}, whose value can be compared to other (experimental and theoretical) estimates. Several unsophisticated parametrisations, differing by the amount of physical information that they embed, are shown to pass this test. An apparently more elaborated parametrisation of form factors, the so-called z-expansion, is at variance with the other models, and we point out some significant shortcomings of this parametrisation for the problem under consideration.Comment: 16 pages, 2 figures. A few references added. Accepted for publication in JoP

    Quark Masses and Renormalization Constants from Quark Propagator and 3-point Functions

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    We have computed the light and strange quark masses and the renormalization constants of the quark bilinear operators, by studying the large-p^2 behaviour of the lattice quark propagator and 3-point functions. The calculation is non-perturbatively improved, at O(a), in the chiral limit. The method used to compute the quark masses has never been applied so far, and it does not require an explicit determination of the quark mass renormalization constant.Comment: LATTICE99 (Improvement and Renormalization) - 3 pages, 2 figure

    Decays of Heavy Mesons

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    We present preliminary results for heavy to light transitions of pseudoscalar mesons, induced by the vector and tensor operators. This lattice study is performed in quenched approximation, by using the nonperturbatively improved Wilson action and operators. We also update the values of the heavy-light meson decay constants.Comment: LATT99(Heavy Quarks), 3 pages, 2 figure

    Lattice calculation of SU(3) flavor breaking ratios in B - anti-B mixing

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    We present an unquenched lattice calculation for the SU(3) flavor breaking ratios of the heavy-light decay constants and the ΔB=2\Delta B = 2 matrix elements. The calculation was performed on 163×3216^3 \times 32 lattices with two dynamical flavors of domain-wall quarks and inverse lattice spacing 1/a=1.69(5)1/a = 1.69(5) GeV. Heavy quarks were implemented using an improved lattice formulation of the static approximation. In the infinite heavy-quark mass limit we obtain fBs/fBd=1.29(4)(6)f_{B_s}/f_{B_d} = 1.29(4)(6), BBs/BBd=1.06(6)(4)B_{B_s}/B_{B_d} = 1.06(6)(4), ξ=1.33(8)(8)\xi = 1.33(8)(8) where the first error is statistical and the second systematic.Comment: 23 pages, 8 figures, RevTeX4; mentioned existence of 1/m_b corrections, minor changes improving readabilit

    B-parameters of the complete set of matrix elements of (Delta B = 2) operators from the lattice

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    We compute on the lattice the ``bag'' parameters of the five (Delta B = 2) operators of the supersymmetric basis, by combining their values determined in full QCD and in the static limit of HQET. The extrapolation of the QCD results from the accessible heavy-light meson masses to the B-meson mass is constrained by the static result. The matching of the corresponding results in HQET and in QCD is for the first time made at NLO accuracy in the MSbar(NDR) renormalization scheme. All results are obtained in the quenched approximation.Comment: 27 pages (5 figures

    Combined Relativistic and static analysis for all Delta B=2 operators

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    We analyse matrix elements of Delta B=2 operators by combining QCD results with the ones obtained in the static limit of HQET. The matching of all the QCD operators to HQET is made at NLO order. To do that we have to include the anomalous dimension matrix up to two loops, both in QCD and HQET, and the one loop matching for all the Delta B=2 operators. The matrix elements of these operators are relevant for the prediction of the B-\bar B mixing, B_s meson width difference and supersymmetric effects in Delta B=2 transitions.Comment: 3 pages, 1 figure. Lattice2001(heavyquark

    Power Corrections to Perturbative QCD and OPE in Gluon Green Functions

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    We show that QCD Green functions in Landau Gauge exhibit sizable O(1/ÎĽ2)O(1/\mu^2) corrections to the expected perturbative behavior at energies as high as 10 GeV. We argue that these are due to a -condensate which does not vanish in Landau gauge.Comment: 3 pages 1 figure lattice2001 (gaugetheories

    A Theoretical Prediction of the Bs-Meson Lifetime Difference

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    We present the results of a quenched lattice calculation of the operator matrix elements relevant for predicting the Bs width difference. Our main result is (\Delta\Gamma_Bs/\Gamma_Bs)= (4.7 +/- 1.5 +/- 1.6) 10^(-2), obtained from the ratio of matrix elements, R(m_b)=/<\bar B_s^0|Q_L|B_s^0>=-0.93(3)^(+0.00)_(-0.01). R(m_b) was evaluated from the two relevant B-parameters, B_S^{MSbar}(m_b)=0.86(2)^(+0.02)_(-0.03) and B_Bs^{MSbar}(m_b) = 0.91(3)^(+0.00)_(-0.06), which we computed in our simulation.Comment: 21 pages, 7 PostScript figure
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