Showing papers on "Pseudoscalar published in 1989"
TL;DR: In this article, a fit to the baryon-octet mass spectrum to the first order of SU (3) breaking indicates unambiguously substantial sea-quark content in the Baryon at rest.
160 citations
CERN1
TL;DR: In this article, the authors used QCD sum rules, low-energy theorems and current algebra for the pseudoscalar nonet to support the hypothesis that the recently observed G(1.6 GeV) meson is a (relatively pure) gluonium state.
Abstract: QCD sum rules, low-energy theorems and current algebra for the pseudoscalar nonet are used to support the hypothesis that the recently observed G(1.6 GeV) meson is a (relatively pure) gluonium state.
104 citations
37 citations
TL;DR: The use of triple-product correlations to signal the presence of $\mathrm{CP}$ violations in decays of charged pseudoscalar mesons is studied and it is pointed out that observation of such correlations in the semileptonic modes is likely to be evidence for new physics.
Abstract: The use of triple-product correlations to signal the presence of $\mathrm{CP}$ violations in decays of charged pseudoscalar mesons is studied. It is pointed out that observation of such correlations in the semileptonic modes is likely to be evidence for new physics. The effect of unitarity phases is discussed and a detailed analysis of the Weinberg Higgs-boson model of $\mathrm{CP}$ violation is carried out for charged $B$ mesons and kaons.
35 citations
TL;DR: In this paper, the instanton-induced contributions to correlation functions in the QCD vacuum were calculated using numerical data on the ensemble of pseudoparticles (PPs) obtained previously, showing how quarks, "hopping" from one PP to another, do form the pseudoscalar mesons, with parameters close to the experimental ones.
26 citations
TL;DR: An unambiguous procedure is employed to construct the electroweak current densities and brings in a parameter, related to the meson-nucleon decay rate, which does not appear in the strong-interaction part of the Lagrangian, which results in a fairly accurate description of the nucleons' properties.
Abstract: We investigate electromagnetic and axial-vector currents and the corresponding form factors as well as meson-nucleon form factors within the framework of a nonlinear chiral Lagrangian constructed by Jain, Johnson, Meissner, Park, and Schechter in Phys. Rev. D 37, 3252 (1988). We employ an unambiguous procedure to construct the electroweak current densities. This brings in a parameter, related to the ..omega --> pi../sup 0/..gamma.. decay rate, which does not appear in the strong-interaction part of the Lagrangian. This results in a fairly accurate description of the nucleons' properties. The effects of coupling to a two-flavor ''eta meson'' are shown to be small.
26 citations
TL;DR: Based on the equivalence theorem of the on-shell S matrix elements independently of nonlinearly realized Goldstone fields, it is proposed a new method to calculate the axion emission rate from NN..-->..NN..pi.. data and the result is compared to the theoretical calculation based on the one-pion-exchange approximation.
Abstract: Based on the equivalence theorem of the on-shell S matrix elements independently of nonlinearly realized Goldstone fields, we clarify the discrepancies raised by the use of the pseudovector derivative and pseudoscalar pion-nucleon couplings in the nucleon-nucleon axion bremsstrahlung process which is often taken as the dominant axion emission mechanism from SN 1987 A. In addition, we propose a new method to calculate the axion emission rate from NN..-->..NN..pi.. data, and we compare the result to the theoretical calculation based on the one-pion-exchange approximation.
20 citations
TL;DR: In this article, the mixing of light-light and light-heavy pseudoscalar mesons was studied and the mixing angles were derived without invoking the diagonalization of the mass matrix.
19 citations
TL;DR: In this article, high energy tree unitarity is investigated in a spontaneously broken N = 1 supergravity theory with a gauge as well as a matter sector through the amplitude for the process gauge boson + girders → gravitino.
17 citations
TL;DR: In this article, it was shown that for the coupling required to explain ge−2 and positronium, a mass of at least 34 keV (175 keV) is required.
16 citations
TL;DR: In this paper, the effects of the large scalar and vector potentials of the relativistic model and of the Dirac-spinor wave functions of the proton and the Λ-hyperon on the calculated quantity were analyzed.
Abstract: We review the results of recent studies and calculations of Λ-hypernuclear excitations via electromagnetic probes [the (e, e′K+) and (γ, K+) reactions]. After discussing the importance of the probe, we present and analyze the theoretical features of a model (based on Feynman diagrams) for studying the process. The special kinematics of the nuclear (e, e′K+) reaction, involving high momentum transfers, is discussed. We then present cross section calculations. Using first a nonrelativistic nuclear structure model, we present results for the exclusive and inclusive electromagnetic hypernuclear excitations and for a large range of nuclear masses. Next, we calculate cross sections using the fully-relativistic form of the transition operator and relativistic Dirac-nuclear-and hypernuclear- structure model. In this context, we analyze the effects of the large scalar and vector potentials of the relativistic model and of the Dirac-spinor wave functions of the proton and the Λ-hyperon, on the calculated quantity. The relativistic-model calculations are presented for both pseudoscalar (PS) and pseudovector (PV) KNΛ vertex couplings and we discuss in detail the different theoretical predictions obtained in the two cases. Throughout the paper, we emphasize several uncertainties regarding the determination of coupling constants, PS vs PV coupling schemes, and relativistic uncertainties. Finally, we present technical and experimental considerations for the study of the (e, e′K+) and (γ, K+) reactions at the continuous electron beam accelerator facility (CEBAF), which is currently under construction in Newport News, Virginia.
TL;DR: In this article, the authors examined the pseudoscalar quark densities of the proton matrix elements of the Nambu-Jona-Lasinio model and showed that the form factor related to the matrix element is considerably quenched with increasing mass of the strange quark.
TL;DR: In this article, the masses and decay constants of pseudoscalar mesons were investigated in the instanton liquid model of the QCD vacuum using the long-wavelength approximation.
TL;DR: In this paper, an extended version of the Nambu-Jona-Lasinio model is supplemented with the 't Hooft determinant and bosonized for an arbitrary number of flavours.
Abstract: An extended version of the Nambu-Jona-Lasinio model is supplemented with the 't Hooft determinant and bosonized for an arbitrary number of flavours. The resulting effective meson lagrangian is in good agreement with the experimental low-energy mesonic data. The presence of the 't Hooft determinant leads to a flavour mixing of the scalar and pseudoscalar mesons with diagonal flavour content. This instanton induced flavour mixing in the scalar and pseudoscalar channel is noticeably effected by the coupling to the vector and axial-vector meson sector. If the latter is taken into account the η−η′ mixing angle is shifted from −31° to −22° in good agreement with the experimental value.
TL;DR: The difference between the pseudoscalar and pseudovector ..pi..N couplings are examined in the context of the nucleonic axion bremsstrahlung rate and a naive use of this coupling gives a different matrix element and overestimates the energy-loss rate of degenerate neutron-star matter via neutron-neutron axion Bremsstahlung.
Abstract: The difference between the pseudoscalar and pseudovector \ensuremath{\pi}N couplings are examined in the context of the nucleonic axion bremsstrahlung rate. With the pseudovector coupling, eight diagrams contribute to the matrix element for axion bremsstrahlung. A naive use of the pseudoscalar coupling for these eight diagrams, on the other hand, gives a different matrix element and overestimates the energy-loss rate of degenerate neutron-star matter via neutron-neutron axion bremsstrahlung typically by an order of magnitude.
TL;DR: Using a nonrelativistic gluon bound-state model, GAMMA(G..--> gamma gamma..), where G is a pseudoscalar, tensor, or scalar digluon, is computed, starting from the amplitudes of the process ..gamma gamma -->..g/Sup */g/sup */ at threshold, the g/sup's being massive constituent gluons.
Abstract: Using a nonrelativistic gluon bound-state model, we compute GAMMA(G..--> gamma gamma..), where G is a pseudoscalar, tensor, or scalar digluon, starting from the amplitudes of the process ..gamma gamma -->..g/sup */g/sup */ at threshold, the g/sup */'s being massive constituent gluons. Those amplitudes are obtained, at lowest order in perturbative QCD, by deriving them from a QED calculation performed many years ago by Constantini, de Tollis, and Pistoni. The unknown parameter (the digluon wave function, or its first or second derivative, at the origin) is determined by using measured values of GAMMA(J/psi..-->..G..gamma..). Our predictions are compared, for various glueball candidates, with present experimental limits.
TL;DR: Using the equivalence theorem, it is shown that the pion mass difference leads to a 3% effect in the pseudovector ..pi..N coupling constants.
Abstract: We investigate the pseudoscalar pion-nucleon constants in the framework of various chiral models of the nucleon. We demonstrate that strong isospin violation (m/sub u/not =m/sub d/) does not lead to a charge dependence of the pion-nucleon vertex as recently reported on the basis of NN scattering data. Using the equivalence theorem, we show that the pion mass difference leads to a 3% effect in the pseudovector ..pi..N coupling constants.
TL;DR: The formalism for the description of Green's functions of composite operators on the nonperturbative vacuum is proposed and the dynamics in the regime with the nontrivial fixed point is discussed.
Abstract: The formalism for the description of Green's functions of composite operators on the nonperturbative vacuum is proposed. In the ladder approximation the formalism is applied to determine Green's functions of the operators F/sub ..mu..//sub ..nu../F/sup ..mu..//sup ..nu../, psi-barlambda/sup a/psi, psi-bar..gamma../sub 5/lambda/sup a/psi in vectorlike gauge theories. The properties of scalar and pseudoscalar bound states in gauge theories and in gauge theories with an additional four-fermion interaction are considered. The dynamics in the regime with the nontrivial fixed point is discussed.
TL;DR: The mass dependence of decay constants for vector and pseudoscalar mesons is calculated using both Wilson and staggered-fermion formulations in quenched lattice QCD and reasonable agreement is found between the two fermion formulations.
Abstract: The mass dependence of decay constants for vector and pseudoscalar mesons is calculated using both Wilson and staggered-fermion formulations in quenched lattice QCD. For low meson masses, the agreement of the two methods is good and the determination of the vector decay constant agrees with experiment. For pseudoscalar heavy-quark--light-quark systems, we find reasonable agreement between the two fermion formulations as long as Ma\ensuremath{\lesssim}1, where M is the meson mass.
TL;DR: In this article, conditions and conditions of validity are presented for three selection rules relevant to the analysis of data indicating the existence of a possible CP -exotic state and to the determination of whether it is a four-quark or hybrid state.
TL;DR: The contribution of fermion and scalar condensates to the photon propagator and pseudoscalar correlation function was evaluated in this article, where the contribution of photon propagators was calculated exactly in their masses.
Abstract: The contribution of fermion and scalar condensates,\(\left\langle {\bar \psi \psi } \right\rangle \) and 〈φ+φ〉 to their propagators is calculated exactly in their masses. The ensuing contributions to the photon propagator and the pseudoscalar correlation function are then evaluated.
TL;DR: In this article, it was shown that to preserve the SU(3)L×SU(3)-R current algebra, it is necessary to have strong isospin violation in heavy quark pseudoscalar densities.
TL;DR: Radiative and pionic transitions between the ground-state pure qq-bar vector and pseudoscalar mesons compatible with observed mass splittings are studied.
Abstract: Radiative and pionic transitions between the ground-state pure qq-bar vector and pseudoscalar mesons compatible with observed mass splittings are studied.
TL;DR: In this paper, the authors considered the quantum field theory of a model of an extended Nambu-Jona-Lasinio type with a QCD based nonlocal fermion current-current interaction which has global SU(Nc) symmetry.
Abstract: We consider the quantum field theory of a model of an extended Nambu-Jona-Lasinio type with a QCD based nonlocal fermion current-current interaction which has global SU(Nc) symmetry. We obtain an exact bosonization of this model in four Euclidean dimensions using auxiliary bilocal fields and discuss the dynamical breakdown of chiral symmetry in the massless fermion limit. A local field bosonization is obtained by decomposing the bilocal fields in terms of complete orthonormal sets of functions with the expansion coefficients, which are local functions, identified as the local meson fields. Retaining the ground state pseudoscalar, vector and pseudovector local fields we obtain a local effective action for this sector of the theory. The derivative expansion of the fermionic determinant necessary to obtain this local action is self-regularizing because of the bilocal substructure present in the model which is manifest in the form factors that are associated with the local fields. In our local action the value of each coefficient depends critically on the underlying fermionic dynamics through these form factors and the vacuum functions. As a consequence of this the vector and pseudovector fields in the theory are best interpreted as simple fermion-antifermion bound states rather than as massive Yang-Mills fields or exotic composites of the pseudoscalars; interpretations that we find are not in general admitted when models such as the GCM are treated correctly. Identifying then the physical vector and pseudovector fields with the linearly transforming chiral partners introduced by the bosonization, we obtain an effective action for this sector of the meson spectrum which predicts values for the kinematic and dynamic quantities associated with these fields.
TL;DR: In this paper, the Coleman-Glashow lambda 3 tadpole scheme for SU(2) mass splittings of hadrons was reviewed and a universal 2% SU( 2) to SU( 3) breaking effect for pseudoscalar and vector mesons and for octet and decuplet baryons was found.
Abstract: For pt.II see ibid., vol.15, p.943, (1989). The authors review the Coleman-Glashow lambda 3 tadpole scheme for SU(2) mass splittings of hadrons and find a universal 2% SU(2) to SU(3) breaking effect for pseudoscalar and vector mesons and for octet and decuplet baryons. Then they compute the SU(2)-broken rotated current divergence sandwiched between nucleon and cascade baryon states built up from SU(6) valence quark wavefunctions and find md-mu approximately 7 to 8 MeV. The same d-u current mass difference also follows from ( rho 0 mod H3tad mod omega mod with vector meson states built up from SU(6) quark wavefunctions.
TL;DR: In this paper, two-loop corrections to the coefficient functions of the condensates were calculated in the QCD sum rules for the light mesons in the vector, scalar and pseudoscalar channels.
Abstract: We calculate two-loop corrections to the coefficient functions of the condensates 〈G2〉0 and in the QCD sum rules for the light mesons in the vector, scalar and pseudoscalar channels, and three-loop corrections to the coefficient function of the condensate 〈G2〉0 in the (pseudo)scalar channel. We find that a renormalization-group analysis casts strong doubts on the feasibility of obtaining correct estimates for the coefficient functions via perturbation theory.
TL;DR: In this article, the asymptotic behavior of the Dirac wave function in a QCD leading-log Coulomb potential was studied and an estimate of the decay constant for pseudoscalar Q q mesons in the region M Q ≳ 0.8 GeV was given.
01 Apr 1989
TL;DR: In this article, the effective non-leptonic Hamiltonian can be expressed in terms of scalar and pseudoscalar local diquark currents, and a QCD sum rule calculation gives a large value for the coupling constant of correlated 0+ 2-quark states -diquarks - to these currents.
Abstract: The effective non-leptonic Hamiltonian can be expressed in terms of scalar and pseudoscalar local diquark currents. A QCD sum rule calculation gives a large value for the coupling constant of correlated 0+ 2-quark states - diquarks - to these currents. Whenever scalar diquarks can contribute to a decay amplitude an enhancement is predicted. Baryon matrix elements relevant for |ΔS| = 1 transitions are computed. For the process K → 2π via a virtual diquark pair a chiral model is applied. The diquark picture gives a semi-quantitative understanding of the |Δ I | = 1 2 enhancement in strange particle decays.
TL;DR: In this paper, a one-loop effective largrangian for the U( N )×U(N ) symmetric Nambu-Jona-Lasinio model is constructed by expanding the fermion determinant around the spontaneously broken vacuum.