Meson Decay Constants Research Articles

Covariant light-front approach for heavy quarkonium: decay constants, P → γγ and V → Pγ

The light-front approach is a relativistic quark model and offers many insights into the internal structures of the hadronic bound states. In this study, we apply the covariant light-front approach to ground-state heavy quarkonium. The pesudoscalar and vector meson decay constants are discussed. We present a detailed study of two-photon annihilation P → γγ and magnetic dipole transition V → Pγ processes. The numerical predictions of the light-front approach are consistent with the experimental data and those in other approaches. The relations of the light-front approach with the other methods are discussed in brief.

QCD with light Wilson quarks on fine lattices (II): DD-HMC simulations and data analysis

In this second report on our recent numerical simulations of two-flavour QCD, we provide further technical details on the simulations and describe the methods we used to extract the meson masses and decay constants from the generated ensembles of gauge fields. Among the topics covered are the choice of the DD-HMC parameters, the issue of stability, autocorrelations and the statistical error analysis. Extensive data tables are included as well as a short discussion of the quark-mass dependence in partially quenched QCD, supplementing the physics analysis that was presented in the first paper in this series.

First nonperturbative test of a relativistic heavy quark action in quenched lattice QCD

We perform a numerical test of a relativistic heavy quark(RHQ) action, recently proposed by Tsukuba group, in quenched lattice QCD at $a\simeq 0.1$ fm. With the use of the improvement parameters previously determined at one-loop level for the RHQ action, we investigate a restoration of rotational symmetry for heavy-heavy and heavy-light meson systems around the charm quark mass. We focused on two quantities, the meson dispersion relation and the pseudo-scalar meson decay constants. It is shown that the RHQ action significantly reduces the discretization errors due to the charm quark mass. We also calculate the S-state hyperfine splittings for the charmonium and charmed-strange mesons and the $D_s$ meson decay constant. The remaining discretization errors in the physical quantities are discussed.

MESON SPECTROSCOPY AND PROPERTIES USING DYSON-SCHWINGER EQUATIONS

We study pseudoscalar and scalar mesons using a practical and symmetry preserving truncation of QCD's Dyson-Schwinger equations. We investigate and compare properties of ground and radially excited meson states. In addition to exact results for radial meson excitations we also present results for meson masses and decay constants from the chiral limit up to the charm-quark mass, e.g., the mass of the χc0(2P) meson.

Electromagnetic corrections in partially quenched chiral perturbation theory

We introduce photons in partially quenched chiral perturbation theory and calculate the resulting electromagnetic loop-corrections at next-to-leading-order (NLO) for the charged meson masses and decay constants. We also present a numerical analysis to indicate the size of the different corrections. We show that several phenomenologically relevant quantities can be calculated consistently with photons which couple only to the valence quarks, allowing the use of gluon configurations produced without dynamical photons.

CURRENT PHYSICS RESULTS FROM STAGGERED CHIRAL PERTURBATION THEORY

We review several results that have been obtained using lattice QCD with the staggered quark formulation. Our focus is on the quantities that have been calculated numerically with low statistical errors and have been extrapolated to the physical quark mass limit and continuum limit using staggered chiral perturbation theory. We limit our discussion to a brief introduction to staggered quarks, and applications of staggered chiral perturbation theory to the pion mass, decay constant, and heavy–light meson decay constants.

ScalarKπform factor and light-quark masses

Recent experimental improvements on $K$-decay data allow for a precise extraction of the strangeness-changing scalar $K\ensuremath{\pi}$ form factor and the related strange scalar spectral function. On the basis of this scalar as well as the corresponding pseudoscalar spectral function, the strange quark mass is determined to be ${m}_{s}(2\text{ }\text{ }\mathrm{GeV})=92\ifmmode\pm\else\textpm\fi{}9\text{ }\text{ }\mathrm{MeV}$. Further taking into account chiral perturbation theory mass ratios, the light up and down quark masses turn out to be ${m}_{u}(2\text{ }\text{ }\mathrm{GeV})=2.7\ifmmode\pm\else\textpm\fi{}0.4\text{ }\text{ }\mathrm{MeV}$ as well as ${m}_{d}(2\text{ }\text{ }\mathrm{GeV})=4.8\ifmmode\pm\else\textpm\fi{}0.5\text{ }\text{ }\mathrm{MeV}$. As a by-product, we also find a value for the Cabibbo angle $|{V}_{us}|=0.2236(29)$ and the ratio of meson decay constants ${F}_{K}/{F}_{\ensuremath{\pi}}=1.203(16)$. Performing a global average of the strange mass by including extractions from other channels as well as lattice QCD results yields ${m}_{s}(2\text{ }\text{ }\mathrm{GeV})=94\ifmmode\pm\else\textpm\fi{}6\text{ }\text{ }\mathrm{MeV}$.

Twisted mass lattice QCD with non-degenerate quark masses

Quantum Chromodynamics on a lattice with Wilson fermions and a chirally twisted mass term is considered in the framework of chiral perturbation theory. For two and three numbers of quark flavours, respectively, with non-degenerate quark masses the pseudoscalar meson masses and decay constants are calculated in next-to-leading order including lattice effects quadratic in the lattice spacing a.

Strange quarks in quenched twisted mass lattice QCD

Two twisted doublets, one containing the up and down quarks and the other containing the strange quark with an $SU(2)$-flavor partner, are used for studies in the meson sector. The relevant chiral perturbation theory is presented, and quenched QCD simulations (where the partner of the strange quark is not active) are performed. Pseudoscalar meson masses and decay constants are computed; the vector and scalar mesons are also discussed. A comparison is made to the case of an untwisted strange quark, and some effects due to quenching, discretization, and the definition of maximal twist are explored.

Holographic model for mesons at finite temperature

A holographic model of QCD at finite temperature is proposed and thermal properties for light mesons are examined in terms of this model. We find interesting temperature dependences of masses and decay constants for several mesons, and Nambu-Goldstone theorem for the chiral symmetry breaking and generalized Gell-Mann-Oakes-Renner relation are assured at finite temperature. Furthermore, we can see in the chiral limit that the speed of the pion in the thermal medium decreases to zero when the temperature approaches to the critical point of quark confinement and deconfinement transition, where the chiral symmetry is restored.

Holographic model at finite temperature with R-charge density

We consider a holographic model of QCD at finite temperature with nonzero chemical potentials conjugate to $R$-charge densities. A critical surface of the confinement-deconfinement phase transition is shown for five-dimensional charged black hole solution given by Behrnd, Cveti\v{c} and Sabra. On a special section of the parameter space, we find an critical curve being similar to the one expected in QCD. We calculate meson spectra and decay constants in the confinement phase of this section to see their temperature and chemical potential dependences. We could assure generalized GellMann-Oakes-Renner relation and the reduction of pion velocity near the critical point.

Three-flavor partially quenched chiral perturbation theory at NNLO for meson masses and decay constants

We discuss Partially Quenched Chiral Perturbation Theory (PQ$\chi$PT) and possible fitting strategies to Lattice QCD data at next-to-next-to-leading order (NNLO) in the mesonic sector. We also present a complete calculation of the masses of the charged pseudoscalar mesons, in the supersymmetric formulation of PQ$\chi$PT. Explicit analytical results are given for up to three nondegenerate sea quark flavors, along with the previously unpublished expression for the pseudoscalar meson decay constant for three nondegenerate sea quark flavors. The numerical analysis in this paper demonstrates that the corrections at NNLO are sizable, as expected from earlier work.

Pseudoscalar meson decay constants and couplings, the Witten–Veneziano formula beyond large [formula omitted], and the topological susceptibility

The QCD formulae for the radiative decays η , η ′ → γ γ , and the corresponding Dashen–Gell-Mann–Oakes–Renner relations, differ from conventional PCAC results due to the gluonic U ( 1 ) A axial anomaly. This introduces a critical dependence on the gluon topological susceptibility. In this paper, we revisit our earlier theoretical analysis of radiative pseudoscalar decays and the DGMOR relations and extract explicit experimental values for the decay constants. This is our main result. The flavour singlet DGMOR relation is the generalisation of the Witten–Veneziano formula beyond large N c , so we are able to give a quantitative assessment of the realisation of the 1 / N c expansion in the U ( 1 ) A sector of QCD. Applications to other aspects of η ′ physics, including the relation with the first moment sum rule for the polarised photon structure function g 1 γ , are highlighted. The U ( 1 ) A Goldberger–Treiman relation is extended to accommodate SU ( 3 ) flavour breaking and the implications of a more precise measurement of the η and η ′ -nucleon couplings are discussed. A comparison with the existing literature on pseudoscalar meson decay constants using large- N c chiral Lagrangians is also made.

Relativistic treatment of the decay constants of light and heavy mesons

Novel relativistic expressions are used to calculate the weak decay constants of pseudoscalar and vector mesons within the constituent quark model. Meson wave functions satisfy the quasipotential equation with the complete relativistic potential. New contributions, coming from the negative-energy quark states, are substantial for the light mesons, significantly decrease the values of their decay constants and, thus, bring them into agreement with experiment. For heavy-light mesons these contribution are much less pronounced, but permit to reduce uncertainties of the predicted decay constants. Their values agree with the results of lattice calculations and experimental data.

Charm mesons with DWF quarks on a quenched 3 GeV lattice

We present some preliminary results on charmed meson spectroscopy from a RIKEN-BNL-Columbia lattice numerical claculations. We use domain-wall fermions (DWF) for all quark flavors including charm. To make this meaningful we use quenched gauge ensemble with lattice cutoff a −1 of about 3 GeV obtained with the DBW2 rectangular improved action. With the strange quark mass estimate of m strange a = 0.030 from the associated kaon sector calculations, we obtain a charm mass estimate of m charm a = 0.360 ( 7 ) by fitting the D s meson mass. With these and additional extrapolations for light quark mass to the chiral limit, we discuss charmed D and D* and charm-strange ( D s and D s J ) mesons with spin-parity J P = 0 ± and 1 ± . We also discuss our preliminary results for the pseudoscalar meson (D and D s ) decay constants.

Decay constants of heavy vector mesons in relativistic Bethe–Salpeter method

In a previous Letter, we computed the decay constants of heavy pseudoscalar mesons in the framework of relativistic (instantaneous) Bethe–Salpeter method (full 0− Salpeter equation), in this Letter, we solve the full 1− Salpeter equation and compute the leptonic decay constants of heavy–heavy and heavy–light vector mesons. The theoretical estimate of mass spectra of these heavy–heavy and heavy–light vector mesons are also presented. Our results for the decay constants and mass spectra include the complete relativistic contributions. We find FDs∗≈375±24, FD∗≈340±23(D∗0,D∗±), FBs∗≈272±20, FB∗≈238±18(B∗0,B∗±), FBc∗≈418±24, FJ/Ψ≈459±28, FΨ(2S)≈364±24, Fϒ≈498±20 and Fϒ(2S)≈366± 27 MeV.

Probing unquenching effects in the gluon polarization in light mesons

We introduce an extension to the ladder truncated Bethe-Salpeter equation for mesons and the rainbow truncated quark Schwinger-Dyson equations which includes quark-loop corrections to the gluon propagator. This truncation scheme obeys the axialvector Ward-Takahashi identity relating the quark self-energy and the Bethe-Salpeter kernel. Two different approximations to the Yang-Mills sector are used as input: the first is a sophisticated truncation of the full Yang-Mills Schwinger-Dyson equations, the second is a phenomenologically motivated form. We find that the spectra and decay constants of pseudoscalar and vector mesons are overall described well for either approach. Meson mass results for charge eigenstate vector and pseudoscalar meson masses are compared to lattice data. The effects of unquenching the system are small but not negligible.

DandDSdecay constants from QCD duality at three loops

We compute the decay constants of the pseudoscalar mesons D and D_{s} using a linear combination of finite energy sum rules which minimize the contribution of the unknown continuum spectral function. We employ the recent three loop calculation of the pseudoscalar two-point function expanded in powers of the running charm quark mass. The theoretical uncertainties arising from the QCD asymptotic expansion are quite relevant in this case due to the relative small scale of the charm mass. We obtain the following results: f_{D}=177 \pm 21 MeV and f_{D_{s}}=205 \pm 22 MeV. These results, within the error bars, are in good agreement with estimates obtained using Borel transform QCD sum rules, but somewhat smaller than results of recent lattice computations.

Measurement of the absolute branching ratio for the [formula omitted] decay with the KLOE detector

We have measured the fully inclusive K+→μ+ν(γ) absolute branching ratio with the KLOE experiment at DAΦNE, the Frascati ϕ-factory. From some 865 283 K+→μ+ν(γ) decays obtained from a sample of ∼5.2×108, ϕ-meson decays, we find BR(K+→μ+νμ(γ))=0.6366±0.0009stat.±0.0015syst., corresponding to an overall fractional error of 0.27%. Using recent lattice results on the decay constants of pseudoscalar mesons one can obtain an estimate for the CKM mixing matrix element |Vus|=0.2223±0.0026.

Masses and decay constants of pseudoscalar mesons to two loops in two-flavor partially quenched chiral perturbation theory

This paper presents a first study of the masses and decay constants of the charged, or flavor-off-diagonal, pseudoscalar mesons to two loops for two flavors of sea-quarks, in Partially Quenched Chiral Perturbation Theory (PQ$\chi$PT). Explicit analytical expressions up to ${\cal O}(p^6)$ in the momentum expansion are given. The calculations have been performed within the supersymmetric formulation of PQ$\chi$PT. A numerical analysis is done to indicate the size of the corrections.