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Showing papers on "Pseudoscalar published in 2004"


Journal ArticleDOI
TL;DR: In this paper, the authors discuss theoretical predictions for the existence of exotic nonquark-model mesons and review prominent experimental candidates, and conclude that some of these states exist, offer their views and discuss crucial issues that need to be investigated both theoretically and experimentally.

298 citations


Journal ArticleDOI
TL;DR: Light scalar mesons are found to fit rather well a diquark-antidiquark description, and the resulting nonet obeys mass formulas which respect, to a good extent, the Okubo-Zweig-Iizuka (OZI) rule.
Abstract: Light scalar mesons are found to fit rather well a diquark-antidiquark description. The resulting nonet obeys mass formulas which respect, to a good extent, the Okubo-Zweig-Iizuka (OZI) rule. OZI allowed strong decays are reasonably reproduced by a single amplitude describing the switch of a $q\overline{q}$ pair, which transforms the state into two colorless pseudoscalar mesons. Predicted heavy states with one or more quarks replaced by charm or beauty are briefly described; they should give rise to narrow states with exotic quantum numbers.

281 citations


Journal ArticleDOI
TL;DR: In this article, it is argued that quenched lattice data indicate the existence of net attraction in the color-octet projection of the quark-antiquark scattering kernel.
Abstract: Features of the dressed-quark-gluon vertex and their role in the gap and Bethe-Salpeter equations are explored. It is argued that quenched lattice data indicate the existence of net attraction in the color-octet projection of the quark-antiquark scattering kernel. The study employs a vertex model whose diagrammatic content is explicitly enumerable. That enables the systematic construction of a vertex-consistent Bethe-Salpeter kernel and thereby an exploration of the consequences for the strong interaction spectrum of attraction in the color-octet channel. With rising current-quark mass the rainbow-ladder truncation is shown to provide an increasingly accurate estimate of a bound state's mass. Moreover, the calculated splitting between vector and pseudoscalar meson masses vanishes as the current-quark mass increases, which argues for the mass of the pseudoscalar partner of the $\ensuremath{\Upsilon}(1S)$ to be above $9.4\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}$. With the amount of attraction suggested by lattice data color-antitriplet diquarks are absent from the strong interaction spectrum.

140 citations


Journal ArticleDOI
TL;DR: Goldstone modes are the only pseudoscalar mesons with a nonzero leptonic decay constant in the chiral limit when chiral symmetry is dynamically broken as mentioned in this paper.
Abstract: Goldstone modes are the only pseudoscalar mesons to possess a nonzero leptonic decay constant in the chiral limit when chiral symmetry is dynamically broken. The decay constants of their radial excitations vanish. These features and aspects of their impact on the meson spectrum are illustrated using a manifestly covariant and symmetry-preserving model of the kernels in the gap and Bethe-Salpeter equations.

133 citations


Journal ArticleDOI
TL;DR: In this article, a resonance dominated Green function is matched with a chiral resonance Lagrangian to determine some of the chiral low-energy constants of O(p 6 ).

111 citations


Journal ArticleDOI
TL;DR: In this article, the first Gegenbauer moment of the lightcone distribution amplitude is calculated by the difference between the average momenta of strange and nonstrange valence quarks in the kaon.
Abstract: We present a new calculation of the first Gegenbauer moment a K of the kaon lightcone distribution amplitude. This moment is determined by the difference between the average momenta of strange and nonstrange valence quarks in the kaon. To calculate a K , QCD sum rule for the diagonal correlation function of local and nonlocal axial-vector currents is used. Contributions of condensates up to dimension six are taken into account, including O(�s)-corrections to the quark-condensate term. We obtain a K = 0.05 ± 0.02, differing by the sign and magnitude from the recent sumrule estimate from the nondiagonal correlation function of pseudoscalar and axialvector currents. We argue that the nondiagonal sum rule is numerically not reliable. Furthermore, an independent indication for a positive a K is given, based on the matching of two different light-cone sum rules for the K → � form factor. With the new interval of a K , we update our previous numerical predictions for SU(3)-violating effects in B (s) → K form factors and charmless B decays.

86 citations


01 May 2004
TL;DR: The induced pseudoscalar coupling is the least well known of the weak couplings of the proton's charged-current interaction as mentioned in this paper, and its measurement represents an important test of quantum chromodynamics at low energies.
Abstract: The induced pseudoscalar coupling ${g}_{p}$ is the least well known of the weak couplings of the proton's charged-current interaction. Its size is dictated by chiral symmetry arguments, and its measurement represents an important test of quantum chromodynamics at low energies. Experiments over the past decade have produced a large body of new data relevant to the coupling ${g}_{p}.$ These data include measurements of radiative and nonradiative muon capture on targets ranging from hydrogen and few-nucleon systems to complex nuclei. The authors review the theoretical underpinnings of ${g}_{p},$ the experimental studies, and the procedures and uncertainties in extracting the coupling from data. They also discuss current puzzles and future opportunities.

79 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of quark-gluon vertex dressing on the ground-state masses of the u/d-quark pseudoscalar, vector and axialvector mesons is considered with the Dyson-Schwinger equations.
Abstract: The effect of quark-gluon vertex dressing on the ground-state masses of the u/d-quark pseudoscalar, vector and axialvector mesons is considered with the Dyson-Schwinger equations. This extends the ladder-rainbow Bethe-Salpeter kernel to two-loops. To render the calculations feasible for this exploratory study, we employ a simple infrared dominant model for the gluon exchange that implements the vertex dressing. The resulting model, involving two distinct representations of the effective gluon exchange kernel, preserves both the axial-vector Ward-Takahashi identity and charge conjugation symmetry. Numerical results confirm that the pseudoscalar meson retains its Goldstone boson character. The vector meson mass, already at a very acceptable value at ladder level, receives only 30 MeV of attraction from this vertex dressing. For the axial-vector states, which are about 300 MeV too low in ladder approximation, the results are mixed: The 1+− state receives 290 MeV of repulsion, but the 1++ state is lowered further by 30 MeV. The exotic channels 0−− and 1−+ are found to have no states below 1.5 GeV in this model.

74 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the spectrum of pseudoscalar and scalar mesons exhibits a quasidegenerate chiral nonet in the energy region around 1.4 GeV whose scalar component has a slightly inverted spectrum.
Abstract: We point out that the spectrum of pseudoscalar and scalar mesons exhibits a quasidegenerate chiral nonet in the energy region around 1.4 GeV whose scalar component has a slightly inverted spectrum. Based on the empirical linear rising of the mass of a hadron with the number of constituent quarks which yields a mass around 1.4 GeV for tetraquarks, we conjecture that this quasichiral nonet arises from the mixing of a chiral nonet composed of tetraquarks with conventional $\overline{q}q$ states. We explore this possibility in the framework of a chiral model assuming a tetraquark chiral nonet around 1.4 GeV with chiral symmetry realized directly. We stress that ${U}_{A}(1)$ transformations can distinguish $\overline{q}q$ from tetraquark states, although it cannot distinguish specific dynamics in the later case. We find that the measured spectrum is consistent with this picture. In general, pseudoscalar states arise as mainly $\overline{q}q$ states but scalar states turn out to be strong admixtures of $\overline{q}q$ and tetraquark states. We work out also the model predictions for the most relevant couplings and calculate explicitly the strong decays of the ${a}_{0}(1450)$ and ${K}_{0}^{*}(1430)$ mesons.

72 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used specific angular distributions in the h→τ+τ−, τ ± →ρ ± ν τ (ν τ ) decay chain to probe mixing angles of scalar-pseudoscalar hττ couplings.

68 citations


Journal ArticleDOI
TL;DR: In this paper, the authors make a theoretical study of the J/psi decays into omegapipi, phipipi and omegaK over bar using the techniques of the chiral unitary approach stressing the importance of the scalar resonances dynamically generated through the final state interaction of the two pseudoscalar mesons.

Journal ArticleDOI
TL;DR: In this paper, two-meson distribution amplitudes for the vector-pseudoscalar pair were introduced, such that the analysis is simplified into the one for two-body decays.
Abstract: We study three-body nonleptonic decays B ! VVP by introducing two-meson distribution amplitudes for the vector-pseudoscalar pair, such that the analysis is simplified into the one for two-body decays. The twist-2 and twist-3 �K two-meson distribution amplitudes, associated with longitudinally

Journal ArticleDOI
TL;DR: In this paper, it was shown that the spectrum of pseudoscalar and scalar mesons exhibits a quasidegenerate chiral nonet in the energy region around 1.4 GeV whose scalar component has a slightly inverted spectrum.
Abstract: We point out that the spectrum of pseudoscalar and scalar mesons exhibits a quasidegenerate chiral nonet in the energy region around 1.4 GeV whose scalar component has a slightly inverted spectrum. Based on the empirical linear rising of the mass of a hadron with the number of constituent quarks which yields a mass around 1.4 GeV for tetraquarks, we conjecture that this quasichiral nonet arises from the mixing of a chiral nonet composed of tetraquarks with conventional $\overline{q}q$ states. We explore this possibility in the framework of a chiral model assuming a tetraquark chiral nonet around 1.4 GeV with chiral symmetry realized directly. We stress that ${U}_{A}(1)$ transformations can distinguish $\overline{q}q$ from tetraquark states, although it cannot distinguish specific dynamics in the later case. We find that the measured spectrum is consistent with this picture. In general, pseudoscalar states arise as mainly $\overline{q}q$ states but scalar states turn out to be strong admixtures of $\overline{q}q$ and tetraquark states. We work out also the model predictions for the most relevant couplings and calculate explicitly the strong decays of the ${a}_{0}(1450)$ and ${K}_{0}^{*}(1430)$ mesons.

Journal ArticleDOI
TL;DR: In this article, the authors compute the hyperfine splitting in heavy quarkonium composed of different flavors in next-to-leading logarithmic approximation using the nonrelativistic renormalization group.

Journal ArticleDOI
TL;DR: In this article, the structure of pseudoscalar mesons was investigated in the framework of the coupled rainbow Schwinger-Dyson equation and ladder Bethe-Salpeter equation with the confining effective potential.

Journal ArticleDOI
TL;DR: In this article, the Lagrangian interactions with a pseudoscalar or pseudovector meson-baryon coupling were employed for photoproduction reactions for Θ +, which was recently observed as a candidate of an exotic five quark state uudd s.

Journal ArticleDOI
TL;DR: In this article, a phenomenological Lagrangian for the decay of the SU(3) nonets of the axial-vector mesons of J{sup PC} = 1{sup +-},1{sup ++} into a vector meson and a pseudoscalar constructed with tensor fields for the vector and axial vector mesons was proposed.
Abstract: We propose a phenomenological Lagrangian for the decay of the SU(3) nonets of the axial-vector mesons of J{sup PC}=1{sup +-},1{sup ++} into a vector meson and a pseudoscalar constructed with tensor fields for the vector and axial-vector mesons. The formulation leads to a good reproduction of the different decay branching ratios and assuming vector meson dominance (VMD) it also leads to good results for the radiative decay of the a{sub 1} into pion and photon, and in agreement with the structure proposed in the chiral tensor formulation of radiative decay of axial-vector mesons. The two SU(3) parameters and the mixing angle of K{sub 1A} and K{sub 1B} needed to give the physical K{sub 1}(1270) and K{sub 1}(1400) resonances are also determined.

Journal ArticleDOI
TL;DR: In this paper, the authors examined the possible existence of new physics beyond the standard model which could modify the branching fractions of the leptonic (mainly tauonic) decays of bottomonium vector resonances below the threshold.
Abstract: In this work, we examine the possible existence of new physics beyond the standard model which could modify the branching fractions of the leptonic (mainly tauonic) decays of bottomonium vector resonances below the threshold. The decay width is factorized as the product of two pieces: (a) the probability of an intermediate pseudoscalar color-singlet state (coupling to the dominant Fock state of the Upsilon via a magnetic dipole transition) and a soft (undetected) photon; (b) the annihilation width of the pair into two leptons, mediated by a non-standard CP-odd Higgs boson of mass about 10 GeV, introducing a quadratic dependence on the lepton mass in the partial width. The process would be unwittingly ascribed to the ϒ leptonic channel thereby (slightly) breaking lepton universality. A possible mixing of the pseudoscalar Higgs and bottomonium resonances is also considered. Finally, several experimental signatures to check out the validity of the conjecture are discussed.

Journal ArticleDOI
TL;DR: In this article, it was shown that the Goldstone mesons have a nonzero leptonic decay constant in the chiral limit when chiral symmetry is dynamically broken, while the decay constants of their radial excitations vanish.
Abstract: A strongly momentum-dependent dressed-quark mass function is basic to QCD. It is central to the appearance of a constituent-quark mass-scale and an existential prerequisite for Goldstone modes. Dyson-Schwinger equation (DSEs) studies have long emphasised this importance, and have proved that QCD's Goldstone modes are the only pseudoscalar mesons to possess a nonzero leptonic decay constant in the chiral limit when chiral symmetry is dynamically broken, while the decay constants of their radial excitations vanish. Such features are readily illustrated using a rainbow-ladder truncation of the DSEs. In this connection we find (in GeV): f_{eta_c(1S)}= 0.233, m_{eta_c(2S)}=3.42; and support for interpreting eta(1295), eta(1470) as the first radial excitations of eta(548), eta'(958), respectively, and K(1460) as the first radial excitation of the kaon. Moreover, such radial excitations have electromagnetic diameters greater than 2fm. This exceeds the spatial length of lattices used typically in contemporary lattice-QCD.

Journal ArticleDOI
TL;DR: By matching 1/m(2) divergences in finite-volume two-point correlation functions of the scalar or pseudoscalar densities with those obtained in chiral perturbation theory, this paper derived a relation between the Dirac operator zero-mode eigenfunctions at fixed non-trivial topology and the low-energy constants of QCD.
Abstract: By matching 1/m(2) divergences in finite-volume two-point correlation functions of the scalar or pseudoscalar densities with those obtained in chiral perturbation theory, we derive a relation between the Dirac operator zero-mode eigenfunctions at fixed non-trivial topology and the low-energy constants of QCD. We investigate the feasibility of using this relation to extract the pion decay constant, by computing the zero-mode correlation functions on the lattice in the quenched approximation and comparing them with the corresponding expressions in quenched chiral perturbation theory.

Journal ArticleDOI
TL;DR: In this paper, the decay constants of the pseudoscalar mesons B and Bs were computed using a special linear combination of finite energy sum rules which minimize the contribution of the unknown continuum spectral function.
Abstract: Using special linear combinations of finite energy sum rules which minimize the contribution of the unknown continuum spectral function, we compute the decay constants of the pseudoscalar mesons B and Bs. In the computation, we employ the recent three loop calculation of the pseudoscalar two-point function expanded in powers of the running bottom quark mass. The sum rules show remarkable stability over a wide range of the upper limit of the finite energy integration. We obtain the following results for the pseudoscalar decay constants: fB = 178±14 MeV and fBs = 200±14 MeV. The results are somewhat lower than recent predictions based on Borel transform, lattice computations or HQET. Our sum rule approach of exploiting QCD quark hadron duality differs significantly from the usual ones, and we believe that the errors due to theoretical uncertainties are smaller.

Journal ArticleDOI
TL;DR: In this paper, the pseudoscalar and vector meson masses and leptonic decay constants, ranging from pions up to c\bar{c} bound states, are discussed.
Abstract: Two-body bound states such as mesons are described by solutions of the Bethe-Salpeter equation. We discuss recent results for the pseudoscalar and vector meson masses and leptonic decay constants, ranging from pions up to c\bar{c} bound states. Our results are in good agreement with data. Essential in these calculation is a momentum-dependent quark mass function, which evolves from a constituent-quark mass in the infrared region to a current-quark mass in the perturbative region. In addition to the mass spectrum, we review the electromagnetic form factors of the light mesons. Electromagnetic current conservation is manifest and the influence of intermediate vector mesons is incorporated self-consistently. The results for the pion form factor are in excellent agreement with experiment.

Journal ArticleDOI
TL;DR: The mass difference between the scalar and pseudoscalar heavy-light mesons is larger for the non-strange states than for the strange ones as discussed by the authors, contrary to experiment, the mass difference in the nonstrange case should be smaller.

Journal ArticleDOI
TL;DR: In this article, wide-angle photoproduction of pseudoscalar mesons is investigated under the assumption of dominance of the handbag mechanism, considering both quark helicity flip and non-flip.
Abstract: Wide-angle photoproduction of pseudoscalar mesons is investigated under the assumption of dominance of the handbag mechanism, considering both quark helicity flip and non-flip. The partonic subprocess, meson photoproduction off quarks, is analysed with the help of a covariant decomposition of the subprocess amplitudes which is independent of a specific meson generation mechanism. As examples of subprocess dynamics, however, the twist-2 as well as two-particle twist-3 contributions are explicitly calculated. Characteristic features of the handbag approach are discussed in dependence upon the relative magnitudes of the invariant functions. Differential cross sections and spin correlations are predicted to show a characteristic behaviour which allows one to test the underlying assumption of handbag dominance.

Journal ArticleDOI
TL;DR: In this paper, the authors considered the supersymmetric extension of the 3-3-1 model with right-handed neutrinos and studied the mass spectra in the scalar and pseudoscalar sectors, and for a given set of the input parameters, they found that the lightest scalar in the model has a mass of 130 GeV.
Abstract: We consider the supersymmetric extension of the 3-3-1 model with right-handed neutrinos. We study the mass spectra in the scalar and pseudoscalar sectors, and for a given set of the input parameters, we find that the lightest scalar in the model has a mass of 130 GeVand the lightest pseudoscalar has mass of 5 GeV. However, this pseudoscalar decouples from the Z 0 at high energy scales since it is almost a

Journal ArticleDOI
TL;DR: In this paper, a χ2 fit based on the decay widths and ratios of these mesons to estimate the effects of inter-mixing was performed, and it was shown that the intermixing has large effects for these decay processes and f 0(1710) is preferred as glueball rather than f0(1500).
Abstract: We analyse the mass spectroscopy of low mass scalar nonet and high mass scalar nonet+glueball and get the result that the strengths of the inter-mixing between low and high mass scalar mesons are very strong and the strengths of mixing for I = 1, 1/2 scalar mesons and those of I = 0 scalar mesons are almost the same. We perform a χ2 fit based on the decay widths and ratios of these mesons to estimate the effects of inter-mixing and get the result that the inter-mixing has large effects for these decay processes and f0(1710) is preferred as glueball rather than f0(1500). Best-fit values for the coupling constants A, A' and A'' which represent the couplings of low mass scalar meson N to two pseudoscalar mesons PP, high mass scalar meson N' to PP and glueball G to PP, respectively are obtained as (A, A', A'') = (4.0 ± 1.1 GeV−1, 1.8 ± 0.3 GeV−1, − 0.64 ± 0.04 GeV−1).

Journal ArticleDOI
TL;DR: In this article, the results of a high-statistics study of scalar and pseudoscalar meson propagators in quenched lattice QCD are presented.
Abstract: The results of a high-statistics study of scalar and pseudoscalar meson propagators in quenched lattice QCD are presented. For two values of lattice spacing, $\ensuremath{\beta}=5.7(a\ensuremath{\approx}.18\mathrm{fm})$ and 5.9 $(a\ensuremath{\approx}.12\mathrm{fm}),$ we probe the light quark mass region using clover improved Wilson fermions with the modified quenched approximation pole-shifting ansatz to treat the exceptional configuration problem. The quenched chiral loop parameters ${m}_{0}$ and ${\ensuremath{\alpha}}_{\ensuremath{\Phi}}$ are determined from a study of the pseudoscalar hairpin correlator. From a global fit to the meson correlators, estimates are obtained for the relevant chiral Lagrangian parameters, including the Leutwyler parameters ${L}_{5}$ and ${L}_{8}.$ Using the parameters obtained from the singlet and nonsinglet pseudoscalar correlators, the quenched chiral loop (QCL) effect in the nonsinglet scalar meson correlator is studied. By removing this QCL effect from the lattice correlator, we obtain the mass and decay constant of the ground state scalar, isovector meson ${a}_{0}.$

Journal ArticleDOI
TL;DR: In this article, the mass and decay constants of light pseudoscalar and scalar mesons within QCD sum rules method are briefly reviewed and compared with the existing experimental data and with the predictions of other theoretical approaches.
Abstract: The calculations of masses and decay constants of the radial excitations of light pseudoscalar and scalar mesons within QCD sum rules method are briefly reviewed. The predictions are based on the $1/N_c$-supported model spectra, which consist of infinite number of infinitely narrow resonances, and on the assumption that the ground states of light scalar mesons may be considered as the $\bar{q}q$-bound states. The results of the studies are compared with the existing experimental data and with the predictions of other theoretical approaches.

Proceedings ArticleDOI
TL;DR: In this paper, the meson spectrum in the framework of a second order quark-antiquark Bethe-Salpeter formalism was studied, and an analytic one loop running coupling constant alpha_s(Q) was used in the calculations.
Abstract: In line with some previous works, we study in this paper the meson spectrum in the framework of a second order quark-antiquark Bethe-Salpeter formalism which includes confinement. An analytic one loop running coupling constant alpha_s(Q), as proposed by Shirkov and Sovlovtsov, is used in the calculations. As for the quark masses, the case of a purely phenomenological running mass for the light quarks in terms of the c. m. momentum is further investigated. Alternatively a more fundamental expression m_P(Q) is introduced for light and strange quarks, combining renormalization group and analyticity requirements with an approximate solution of the Dyson-Schwinger equation. The use of such running coupling constant and masses turns out to be essential for a correct reproduction of the the light pseudoscalar mesons.

Journal ArticleDOI
TL;DR: In this paper, the value of the quark condensate from quenched QCD simulations on the lattice was determined by using the Gell-Mann-Oakes-Renner (GMOR) formula and comparing the OPE prediction for the Goldstone pole contribution to the pseudoscalar vertex.