Showing papers on "Pseudoscalar published in 2003"
TL;DR: In this article, a comprehensive study of exclusive hadronic B -meson decays into final states containing two pseudoscalar mesons (PP) and a vector meson (PV) is presented.
797 citations
TL;DR: In this paper, the total cross section for direct production of the Higgs boson in hadron collisions at next-to-next-toleading order (NNLO) in perturbative QCD was computed.
Abstract: We compute the total cross section for direct production of the pseudoscalar Higgs boson in hadron collisions at next-to-next-to-leading order (NNLO) in perturbative QCD. The $\mathcal{O}({\ensuremath{\alpha}}_{s}^{2})$ QCD corrections increase the NLO production cross section by approximately 20--30%.
158 citations
TL;DR: In this paper, the odd-intrinsic-parity effective lagrangian of QCD is analyzed for processes involving one pseudoscalar with vector mesons described in terms of antisymmetric tensor fields.
Abstract: We analyse the most general odd-intrinsic-parity effective lagrangian of QCD valid for processes involving one pseudoscalar with vector mesons described in terms of antisymmetric tensor fields. Substantial information on the odd-intrinsic-parity couplings is obtained by constructing the vector-vector-pseudoscalar Green's three-point function, at leading order in 1/NC, and demanding that its short-distance behaviour matches the corresponding OPE result. The QCD constraints thus enforced allow us to predict the decay amplitudes ω→πγ and ρ→πγ, and the (p6) corrections to π→γγ. Noteworthy consequences concerning the vector meson dominance assumption in the decay ω→3π are also extracted from the previous analysis.
129 citations
TL;DR: In this article, the Darboux transformation operator is applied to the Dirac equation and the following aspects are investigated: factorization of a polynomial of Dirac Hamiltonians, quadratic supersymmetry, closed extension of transformation operators, chains of transformations, and finally particular cases of pseudoscalar and scalar potentials.
91 citations
TL;DR: In a continuation of an ongoing program, this article used staggered chiral perturbation theory to calculate the one-loop chiral logarithms and analytic terms in the pseudoscalar meson leptonic decay constants.
Abstract: In a continuation of an ongoing program, we use staggered chiral perturbation theory to calculate the one-loop chiral logarithms and analytic terms in the pseudoscalar meson leptonic decay constants ${f}_{{\ensuremath{\pi}}_{5}^{+}}$ and ${f}_{{K}_{5}^{+}}.$ We consider the partially quenched, ``full QCD'' (with three dynamical flavors), and quenched cases.
86 citations
TL;DR: The induced pseudoscalar coupling is the least well known of the weak couplings of the proton's charged-current interaction as discussed by the authors, 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.
81 citations
TL;DR: In this article, the relativistic quark model is used to estimate the two-photon decay rates of pseudoscalar, scalar and tensor states of charmonium and bottomonium.
Abstract: Two-photon decay rates of pseudoscalar, scalar and tensor states of charmonium and bottomonium are calculated in the framework of the relativistic quark model. Both relativistic effects and one-loop radiative corrections are taken into account. The obtained results are compared with other theoretical predictions and available experimental data.
69 citations
TL;DR: In this paper, it was shown that using an appropriately chosen renormalization condition one can have consistent power counting for multi-loop diagrams within the relativistic baryon chiral perturbation theory.
Abstract: In the simple model of interacting pseudoscalar and fermion fields it is demonstrated that using an appropriately chosen renormalization condition one can have consistent power counting for multi-loop diagrams within the relativistic baryon chiral perturbation theory. Explicit calculations are performed for a two-loop diagram contributing to fermion self-energy.
48 citations
TL;DR: In this article, the behavior of neutral pseudoscalar mesons π 0, η and η ′ in hot and dense matter is investigated, in the framework of the three flavor Nambu-Jona-Lasinio model.
48 citations
TL;DR: In this paper, the decay of a vector meson to two pseudoscalar mesons on the lattice with $N_f=2$ flavours of sea quark was explored.
48 citations
TL;DR: In this paper, a connection between the infrared limit of the QCD Dirac operator's spectrum and the quark condensate appearing in the operator product expansion was made. But the connection was not verified via comparison with a lattice-QCD simulation.
Abstract: A continuum expression for the trace of the massive dressed-quark propagator is used to explicate a connection between the infrared limit of the QCD Dirac operator's spectrum and the quark condensate appearing in the operator product expansion. This connection is verified via comparison with a lattice-QCD simulation. The pseudoscalar vacuum polarization provides a good approximation to the condensate over a larger range of current-quark masses.
TL;DR: A dramatic effect related to the loss of unitarity, which is naturally explained in the instanton picture, cannot be explained in a Dyson-Schwinger equations approach, if one assumes a vector quark-gluon coupling.
Abstract: We perform a study of the nonperturbative dynamics of the light-quark sector of QCD, based on some recent results of lattice simulations with chiral fermions. We analyze some correlators that are designed to probe the Dirac structure of the quark-quark interaction at different scales. We show that, in the nonperturbative regime, such an interaction contains very large scalar and pseudoscalar components. We observe quantitative agreement between lattice QCD results and the predictions of the instanton liquid model. Moreover, we study how the quark-quark interaction is modified, when quark loops are suppressed. We observe a dramatic effect related to the loss of unitarity, which is naturally explained in the instanton picture. Such an effect cannot be explained in a Dyson-Schwinger equations (DSE) approach, if one assumes a vector quark-gluon coupling.
TL;DR: In this paper, the decay constants for the heavy-light pseudoscalar mesons in the quenched approximation and continuum limit of lattice QCD were derived within the Schrodinger functional framework.
TL;DR: The three-loop anomalous dimensions of the nonrelativistic vector and pseudoscalar currents are determined, revealing the structure of the high-order perturbative corrections in the heavy-quarkonium production and annihilation rates.
Abstract: We calculate the O(alpha(3)(s)ln(alpha(s)) contributions to the heavy-quarkonium production and annihilation rates. Our result sheds new light on the structure of the high-order perturbative corrections and opens a new perspective for a high-precision theoretical analysis. We also determine the three-loop anomalous dimensions of the nonrelativistic vector and pseudoscalar currents.
TL;DR: In this paper, the mass spectrum of the bottom-charmed Bc meson system and spin-dependent splittings from the Schrodinger equation using the shifted-large-N expansion technique were computed.
Abstract: In the framework of potential models for heavy quarkonium, we compute the mass spectrum of the bottom-charmed Bc meson system and spin-dependent splittings from the Schrodinger equation using the shifted-large-N expansion technique. The masses of the lightest vector and pseudoscalar Bc states as well as the higher states below the threshold are estimated. Our predicted result for the ground state energy is MeV and are generally in exact agreement with earlier calculations. Calculations of the Schrodinger energy eigenvalues are carried out up to the third order of the energy series. The parameters of each potential are adjusted to obtain best agreement with the experimental spin-averaged data (SAD). Our findings are compared with the observed data and with the numerical results obtained by other numerical methods.
TL;DR: In this paper, the wave function equations and their numerical solutions for two fermion bound systems were presented, and the results were compared with the nonrelativistic solutions.
Abstract: In the light-front dynamics, the wave function equations and their numerical solutions, for two fermion bound systems, are presented. Analytical expressions for the ladder one-boson exchange interaction kernels corresponding to scalar, pseudoscalar, pseudovector, and vector exchanges are given. Different couplings are analyzed separately and each of them is found to exhibit special features. The results are compared with the nonrelativistic solutions.
TL;DR: In this paper, the Dirac equation is solved for a pseudoscalar Coulomb potential in a two-dimensional world and an infinite sequence of bounded solutions are obtained, in sharp contrast with those ones obtained in 3+1 dimensions where no bound-state solutions are found.
TL;DR: In this article, the authors show that after HERA has been decommissioned, there arises a unique opportunity for searches for very light scalar or pseudoscalar particles beyond the Standard Model which have, so far, remained undetected, due to their very weak coupling to ordinary matter.
TL;DR: In this article, the problem of confinement of neutral fermions in two-dimensional space-time is approached with a pseudoscalar double-step potential in the Dirac equation.
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 to test the underlying assumption of handbag dominance.
TL;DR: In this article, the coupling strengths of mixing between low and high mass scalar mesons are analyzed and the decay widths and decay ratios of these mesons were analyzed, and it was shown that the coupling constants for glueball mesons and pseudoscalar meson are almost the same.
Abstract: We analyze the mass spectroscopy of low and high mass scalar mesons and get the result that the coupling strengths of the 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 same. Next, we analyze the decay widths and decay ratios of these mesons and get the results that the coupling constants $A'$ for $I=1, 1/2$ which represents the coupling of high mass scalar meson $N'$ -> two pseudoscalar mesons $PP$ are almost same as the coupling $A'$ for the I=0. On the other hand, the coupling constant $A$ for $I=1, I=1/2$ which represents the low mass scalar meson $N$ -> $PP$ are far from the coupling constant $A$ for I=0. We consider a resolution for this discrepancy. Coupling constant $A''$ for glueball $G$ -> $PP$ is smaller than the coupling $A'$. $\theta_P$ is $40^\circ \sim 50^\circ$.
TL;DR: In this article, a Gaussian sum-rule analysis of pseudoscalar gluonium states was proposed and the Laplace sum-rules provided corroborating evidence in support of the approximate to 2.7 GeV mass scale.
TL;DR: In this article, the problem of scattering of neutral fermions in two-dimensional space-time is approached with a pseudoscalar potential step in the Dirac equation, and some unexpected aspects of the solutions beyond the absence of Klein\'{}s paradox are presented.
Abstract: The problem of scattering of neutral fermions in two-dimensional space-time is approached with a pseudoscalar potential step in the Dirac equation. Some unexpected aspects of the solutions beyond the absence of Klein\'{}s paradox are presented. An apparent paradox concerning the uncertainty principle is solved by introducing the concept of effective Compton wavelength. Added plausibility for the existence of bound-state solutions in a pseudoscalar double-step potential found in a recent Letter is given.
TL;DR: In this paper, the problem of scattering of neutral fermions in two-dimensional spacetime is approached with a pseudoscalar potential step in the Dirac equation, and some unexpected aspects of the solutions beyond the absence of Klein's paradox are presented.
Posted Content•
03 Jul 2003
TL;DR: In this article, the decay constants for the heavy-light pseudoscalar mesons in the quenched approximation and continuum limit of lattice QCD were derived within the Schrodinger functional framework.
Abstract: We compute the decay constants for the heavy--light pseudoscalar mesons in the quenched approximation and continuum limit of lattice QCD. Within the Schrodinger Functional framework, we make use of the step scaling method, which has been previously introduced in order to deal with the two scale problem represented by the coexistence of a light and a heavy quark. The continuum extrapolation gives us a value $f_{B_s} = 192(6)(4)$ MeV for the $B_s$ meson decay constant and $f_{D_s} = 240(5)(5)$ MeV for the $D_s$ meson.
TL;DR: In this paper, the dependence of the T-odd correlation on the effective Lagrangian parameters in the pseudovector and scalar sectors was analyzed and it was shown that Todd correlation studies will not allow one to improve current restrictions on the parameters of models beyond the standard model.
Abstract: The dependence of the T-odd correlation on the effective Lagrangian parameters in the ${K}^{+}\ensuremath{\rightarrow}\ensuremath{\pi}l\ensuremath{
u}\ensuremath{\gamma},l=e,\ensuremath{\mu},$ decays is analyzed. It is shown that the observable introduced is a perspective in the search for new physics in the vector and pseudovector sectors of the Lagrangian. As for the scalar and pseudoscalar sectors, T-odd correlation studies will not allow one to improve current restrictions on the parameters of models beyond the standard model.
TL;DR: Charmonium sum rules for pseudoscalar 0−+ state ηc(1S) were analyzed within perturbative QCD and operator product expansion as discussed by the authors. But the sensitivity of the results to various approximations for the massive 3-loop pseudOScalar correlator is discussed.
Abstract: Charmonium sum rules for pseudoscalar 0−+ state ηc(1S) are analyzed within perturbative QCD and Operator Product Expansion. The perturbative part of the pseudoscalar correlator is considered at αs2 order and the contribution of the gluon condensate G2 is taken into account with αs correction. The OPE series includes the operators of dimension D = 6,8 computed both in the instanton and factorization model. The method of moments in scheme allows to establish acceptable values of the charm quark mass and gluon condensate, using the experimental mass of ηc. In result of the analisys the charm quark mass is found to be c = 1.26±0.02 GeV independently of the condensate value. The sensitivity of the results to various approximations for the massive 3-loop pseudoscalar correlator is discussed.
TL;DR: In this paper, the authors present results on strong two-body decay widths of light for pseudoscalar and scalar mesons calculated in a covariant quark model, based on the Bethe-Salpeter equation in its instantaneous approximation.
Abstract: In this paper, we present results on strong two-body decay widths of light $q\bar q$
mesons calculated in a covariant quark model. The model is based on the Bethe-Salpeter equation in its instantaneous approximation and has already been used for computing the complete meson mass spectrum and many electroweak decay observables. Our approach relies on the use of a phenomenological confinement potential with an appropriate spinorial Dirac structure and ‘t Hooft’s instanton-induced interaction as a residual force for pseudoscalar and scalar mesons. The transition matrix element for the decay of one initial meson into two final mesons is evaluated in lowest order by considering conventional decays via quark loops as well as Zweig-rule-violating instanton-induced decays generated by the six-quark vertex of ‘t Hooft’s interaction; the latter mechanism only contributes if all mesons in the decay have zero total angular momentum. We show that the interference of both decay mechanisms plays an important role in the description of the partial widths of scalar and pseudoscalar mesons.
01 May 2003
TL;DR: In this paper, the form factors for the semileptonic decays of heavy pseudoscalar to a light vector meson are discussed, in particular for D → K* and B → π modes.
Abstract: New (preliminary) results for the form factors relevant for the semileptonic decays of heavy pseudoscalar to a light vector meson are presented. In particular, we discuss the form factors forD → K* andB → π modes.
TL;DR: In this paper, the structure of the SU(3) octet and decuplet baryons employing a constituent chiral quark model was investigated and the mass differences between positive and negative parity states were well reproduced.
Abstract: We investigate the structure of the SU(3) octet and decuplet baryons employing a constituent chiral quark model. We solve the ground and s- and p-wave excited states of the three-quark system with many range Gaussian bases. This method, which we employ here, has been shown to work quite nicely to describe the structure of the SU(3) s-wave baryons. In this work, we extend our research to the SU(3) p-wave baryons including the tensor term. It is found that the mass differences between positive and negative parity states are well reproduced. It is also found that the pseudoscalar (ps) meson exchange potential plays a very important role to lower the mass of the nucleon resonance ${N}^{*}(1440)$ (Roper). We also discuss how the semirelativistic approach works in the chiral quark model and how to treat the potential terms consistently in the semirelativistic approach.