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We correct Eq. (1) of the original paper, where the term. [ABSTRACT FROM AUTHOR]

We discuss the leptonic decay constants of heavy-light mesons by means of Borel QCD sum rules in the local-duality (LD) limit of infinitely large Borel mass parameter. In this limit, for an appropriate choice of the invariant structures in the QCD correlation functions, all vacuum-condensate contributions vanish and all nonperturbative effects are contained in only one quantity, the effective threshold. We study properties of the LD effective thresholds in the limits of large heavy-quark mass mQ and small light-quark mass mq. In the heavy-quark limit, we clarify the role played by the radiative corrections in the effective threshold for reproducing the pQCD expansion of the decay constants of pseudoscalar and vector mesons. We show that the dependence of the meson decay constants on mq arises predominantly (at the level of 70-80%) from the calculable mq-dependence of the perturbative spectral densities. Making use of the lattice QCD results for the decay constants of nonstrange and strange pseudoscalar and vector heavy mesons, we obtain solid predictions for the decay constants of heavy-light mesons as functions of mq in the range from a few to 100 MeV and evaluate the corresponding strong isospin-breaking effects: fD+-fD0=(0.96±0.09)MeV, fD∗+-fD∗0=(1.18±0.35)MeV, fB0-fB+=(1.01±0.10)MeV, fB∗0-fB∗+=(0.89±0.30)MeV. [ABSTRACT FROM AUTHOR]

We present a study of the strong isospin-breaking (IB) effect, due in QCD to the difference between u - and d -quark masses, in the leptonic decay constants of charmed and beauty pseudoscalar and vector mesons using the method of QCD sum rules. We apply the sum-rule analysis to the decay constants of mesons containing one heavy quark and one light quark with the light mass in the range from the average u / d quark mass to the strange-quark mass. We then analyse the dependence of the decay constants on the light-quark mass and extract with good accuracy the IB ratios of decay constants at leading order in the mass difference ( m d − m u ) , obtaining: ( f D + − f D 0 ) / f D = 0.0047 ( 6 ) , ( f D ⁎ + − f D ⁎ 0 ) / f D ⁎ = 0.0068 ( 9 ) , ( f B 0 − f B + ) / f B = 0.0047 ( 6 ) , and ( f B ⁎ 0 − f B ⁎ + ) / f B ⁎ = 0.0045 ( 5 ) , which yield: f D + − f D 0 = 0.97 ± 0.13 MeV , f D ⁎ + − f D ⁎ 0 = 1.73 ± 0.27 MeV , f B 0 − f B + = 0.90 ± 0.13 MeV , f B ⁎ 0 − f B ⁎ + = 0.81 ± 0.11 MeV . In the case of the D -meson our finding is consistent with recent lattice QCD results, whereas it is much lower in the case of the B -meson showing a tension of ≈3 standard deviations. [ABSTRACT FROM AUTHOR]

We present an ab initio study of inclusive semileptonic decays of heavy mesons from lattice QCD. Our approach is based on a recently proposed method, that allows one to address the study of these decays from the analysis of smeared spectral functions extracted from four-point correlators on the lattice, where the smearing is defined in terms of the phase-space integration relevant to the inclusive decays. We present results obtained from gauge-field ensembles from the JLQCD and ETM collaborations, and discuss their relation with theoretical predictions from the operator-product expansion. [ABSTRACT FROM AUTHOR]

We present a sum-rule calculation of the decay constants of the charmed vector mesons D⁎ and Ds⁎ from the two-point correlator of vector currents. First, we show that the perturbative expansion in terms of the pole mass exhibits no sign of convergence whereas the reorganization of this expansion in terms of the MS¯ mass leads to a distinct hierarchy. Second, making use of the operator product expansion in terms of the MS¯ mass, we determine the decay constants of the D⁎ and Ds⁎ mesons with an emphasis on the uncertainties in these theoretically predicted quantities related both to the input QCD parameters and to the limited accuracy of the method of sum rules. Our results are fD⁎=(252.2±22.3OPE±4syst) MeV and fDs⁎=(305.5±26.8OPE±5syst) MeV. For the ratios of the vector-to-pseudoscalar decay constants we report fD⁎/fD=1.221±0.080OPE±0.008syst and fDs⁎/fDs=1.241±0.057OPE±0.007syst. [ABSTRACT FROM AUTHOR]