Showing papers on "Pseudoscalar published in 1991"
TL;DR: In this paper, a search has been performed for weakly interacting neutral light scalar and pseudoscalar particles in a proton beam dump experiment, and limits on the mass and life-time of these particles are set in the frame of the Standard Model and its minimal supersymmetric extension.
Abstract: A search has been performed for weakly interacting neutral light scalar and pseudoscalar particles in a proton beam dump experiment. No positive signal is observed. Limits on the mass and life-time of these particles are set in the frame of the Standard Model and its minimal supersymmetric extension. The Higgs particle of theSU2L×U1 Standard Theory is excluded for masses in the range 1 MeV
168 citations
TL;DR: The equations give an analytic solution for a zero-mass pseudoscalar bound state in the case of exact chiral symmetry, and also reduce to the familiar, highly successful nonrelativistic linear potential models in the limit of heavy-quark mass and lightly bound systems.
Abstract: We introduce a new model of mesons as quark-antiquark bound states. The model is covariant, confining, and chirally symmetric. Our equations give an analytic solution for a zero-mass pseudoscalar bound state in the case of exact chiral symmetry, and also reduce to the familiar, highly successful nonrelativistic linear potential models in the limit of heavy-quark mass and lightly bound systems. In this fashion we are constructing a unified description of all the mesons from the {pi} through the {Upsilon}. Numerical solutions for other cases are also presented.
62 citations
[...]
TL;DR: Theoretical predictions on decay properties of the simplest particle containing more than one heavy quark, the pseudoscalar, are presented in this article, where some channels that should present a distinctive signature are discussed in more detail.
Abstract: Theoretical predictions on decay properties of the simplest particle containing more than one heavy quark, the pseudoscalar
$$(\bar bc)$$
mesonB
+
, are presented. Some channels that should present a distinctive signature are discussed in more detail.
55 citations
TL;DR: A spatially flat cosmological model dominated by a massive scalar (or pseudoscalar) field with the scalar field potential, which is a tractable approximation of the macrophysics of both the late-time axion-dominated scenario as well as the early-time reheating'' subscenario of the inflation picture.
Abstract: A spatially flat cosmological model dominated by a massive scalar (or pseudoscalar) field ($\ensuremath{\Phi}$) with the scalar field potential $V(\ensuremath{\Phi})={m}^{2}{(\ensuremath{\Phi}\ensuremath{-}{\ensuremath{\Phi}}^{(2)})}^{2}$ (where ${\ensuremath{\Phi}}^{(2)}$ is the value of the scalar field at which the potential vanishes), in the limit in which the length scale corresponding to the scalar field mass $m$ is very much smaller than length scales of cosmological interest (and, in particular, the length scale set by the Hubble parameter), is a tractable approximation of the macrophysics of both the late-time axion-dominated scenario as well as the early-time "reheating" subscenario of the inflation picture. Extending techniques we have previously developed, we derive solutions of the synchronous-gauge relativistic linear perturbation equations which govern the evolution of spatial irregularities, about a spatially homogeneous and isotropic background, in this model.
42 citations
TL;DR: In this article, a bosonized version of the generalized SU(3) Nambu-Jona-Lasinio model including scalar, pseudoscalar, vector and axial couplings is considered up to one quark loop in the context of chiral perturbation theory.
40 citations
TL;DR: In this article, a relativistic Hartree-Fock approach is used to study the magnetic susceptibility of a pure neutron system at relevant densities in neutron stars, and several combinations of mesons and couplings are used.
38 citations
TL;DR: An effective lagrangian which simultaneously describes interactions of scalar, pseudoscalar, vector and axial-vector mesons as well as diquarks including meson and diquark mixing effects is obtained from an extended QCD-motivated Nambu-Jona-Lasinio model as mentioned in this paper.
33 citations
TL;DR: Theoretical ideas of the fifth force(s) are reviewed, placing emphasis on the issue of how one can derive the two most important properties: the coupling strength roughly comparable with, or somewhat weaker than, gravity and the force-range of a macroscopic distance as mentioned in this paper.
Abstract: Theoretical ideas of the fifth force(s) are reviewed, placing emphasis on the issue of how one can derive the two most important properties: the coupling strength roughly comparable with, or somewhat weaker than, gravity and the force-range of a macroscopic distance. Dilaton models, five-dimensional theory, and models of scalar fields induced from pseudoscalar fields as Nambu-Goldstone bosons of internal symmetries via CP violation are reanalyzed critically. All of these theories aim at predicting new types of phenomena to probe physics characterized by mass scales much higher than is accessible by other conventional means. Most of the theoretical predictions are shown to be consistent with effects expected to be discovered below the present experimental upper bounds. We are still waiting for more experiments with better sensitivity.
29 citations
TL;DR: In this article, the possibility of producing light pseudoscalar Higgs bosons, which naturally appear in extensions of the standard model, is analyzed for Z decays and the range of masses and mixing angles that can be explored at LEP is estimated.
28 citations
CERN1
TL;DR: In this paper, an expression for the abnormal intrinsic parity effective action is derived to all orders in terms of only one set of Seeley-DeWitt coefficients for the case of pseudoscalar decays into a photon and a charged lepton pair.
24 citations
TL;DR: The signals associated with two Z 0 decay modes, Z 0 →Sff,Pff, where S(P) is a massless scalar (pseudoscalar) particle present in this theory, and f is a quark or a lepton, are discussed.
Abstract: Supergravity theory with a superlight gravitino (of mass∼m W 2 M P1 −1 ) leads to many interesting Z 0 decay modes which are not present in the standard model or in the usual supergravity theory. We discuss the signals associated with two such decay modes, Z 0 →Sff,Pff, where S(P) is a massless scalar (pseudoscalar) particle present in this theory, and f is a quark or a lepton. Lack of observation of this mode in the current measurements at the CERN e + e − collider LEP leads to a lower bound on the gravitino mass of 10 −14 GeV.
TL;DR: In this article, a detailed analysis of the spin dependent parity violating electron-nucleon potential generated by the hyperfine coupling perturbation upon the pseudoscalar interaction of the electron with the weak charge of the nucleus is presented.
TL;DR: In this paper, the pseudoscalar mesons at the meson poles were considered and the estimated masses of these mesons fix the values of the coupling constants of the effective lagrangian.
TL;DR: The pseudoscalar πNN mixing parameter x = 0.24±0.06 and the strength of the scalar meson field for pions was determined from pionic atoms as discussed by the authors.
TL;DR: In this paper, the authors investigated the polarization variables in Λb→Λc+V− and Λ b→Κc+P− decays, where V is a vector meson and P is a pseudoscalar, and presented estimates for the absolute rates in several channels.
01 Jun 1991
TL;DR: In this paper, the authors discuss the light meson spectrum, with special emphasis on hadronic mass shifts related to thresholds, and discuss the puzzle of the scalar mesons a 0 (980), a 0 /S(1322), and ƒ 0 (975).
Abstract: We discuss the light meson spectrum, with special emphasis on hadronic mass shifts related to thresholds. In particular we discuss the puzzle of the scalar mesons a 0 (980), a 0 /S(1322) and ƒ 0 (975) and comment on the K ∗ (1410) and the K ∗ (1680) . We also emphasize that, as data have improved, the fine-splitting of light qq resonances well above the first threshold seems to be systematically smaller than previous model estimates. This suggests that hadronic self-energy mass shifts are at least as important as the one-gluon exchange in understanding the spectrum. Apart from providing a possible resolution to the puzzle of the light scalars one can then also within the pseudoscalar sector understand better the dual role of the pion as both a Nambu-Goldstone boson and a 1 S 0 q q state.
TL;DR: In this paper, the production of intermediate-mass Higgs bosons in strong electromagnetic fields prevailing in ultrarelativistic heavy-ion collisions is studied and an impact parameter dependent equivalent photon method starting from the gamma gamma to H vertex is developed.
Abstract: The production of intermediate-mass Higgs bosons in strong electromagnetic fields prevailing in ultrarelativistic heavy-ion collisions is studied. To exclude the contribution of central collisions to the production cross section the authors develop an impact parameter dependent equivalent photon method starting from the gamma gamma to H vertex for a scalar boson as well as for a pseudoscalar boson. For an assumed scalar Higgs mass of mH=100 GeV they obtain a reduced cross section sigma H=57 Pb for a Pb-Pb collision at LHC energies with gamma =3500 and sigma H=450 Pb at SSC energies with gamma =8000, which are by a factor of 2.1 and 1.5 smaller than the corresponding original Weizsacker (1934)-Williams (1933) cross sections.
01 Jan 1991
TL;DR: In this article, the SU (3) extension of the Skyrme model with vector mesons in the collective quantization scheme was studied and the effect of the strange excitations on the corresponding moment of inertia was found to be small.
20 May 1991
TL;DR: In this article, the decay constants of heavy pseudoscalar mesons (P) were calculated using the static approximation for the heavy quark propagator and the conventional technique where the decay constant was obtained from fully propagating quark fields.
Abstract: Results of two different calculations of the decay constants (fP) of heavy pseudoscalar mesons (P) are presented. The first calculation uses the static approximation for the heavy-quark propagator, and the second uses the conventional technique where the decay constants are obtained from fully propagating quark fields. Both methods give a substantial negative correction to the asymptotic scaling law fP√MP = constant, at the mass of the charm quark. This is the main result of this talk. The result for the decay constant using the static quark method is however significantly larger than that obtained using the conventional method. A discussion of the systematic errors likely to be responsible for this difference is presented, together with a description of work in progress designed to reduce these errors.
20 May 1991
TL;DR: In this article, the pseudoscalar B-meson decay constant fB was derived by considering the matrix of correlators between local and non-local Qq operators.
Abstract: Using the static approximation for the b-quark, we discuss a lattice calculation of the pseudoscalar B-meson decay constant fB. We test the factorization of the residue of the ground state B-meson pole by considering the matrix of correlators between local and nonlocal Qq operators. Calculation of the B-meson wavefunction is discussed.
TL;DR: By means of the real-time temperature Green function method, this paper extended OPEP with pseudovector coupling and pseudoscalar coupling to finite density and finite temperature and found that the density effects on the effective mass of pion and OPEP are considerable at low temperature.
Abstract: By means of the real-time temperature Green function method, the authors extend the one-pion exchange potential (OPEP) with pseudovector coupling and pseudoscalar coupling to finite density and finite temperature After summing all the bubble diagrams of the exchange of the pion, they find that the density effects on the effective mass of pion and OPEP are considerable at low temperature The density effects and the temperature effects of the OPEP are compared
TL;DR: A relativistic kinetic equation with self-consistent mean field is derived for a field theory of nucleons coupled to neutral scalar and vector mesons and the collective modes of nuclear matter are studied.
Abstract: A relativistic kinetic equation with self-consistent mean field is derived for a field theory of nucleons coupled to neutral scalar and vector mesons. Contrary to previous approaches, our mean field includes the contribution of exchange forces. Due to the exchange terms, the mean field contains tensor, pseudoscalar, and pseudovector components, in addition to the scalar and vector components. By means of this kinetic equation the collective modes of nuclear matter are studied. Because exchange terms are not neglected, the kinetic equation presents additional solutions which correspond to oscillations of the spin density. The longitudinal spin-density wave becomes a tachyon for values of the Fermi momentum ${\mathit{p}}_{\mathit{F}}$g2.87 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$. This fact is related to a spontaneous symmetry breaking: At large baryon densities the minimum of the energy density corresponds to a nonisotropic phase of nuclear matter.
TL;DR: In this paper, the coefficients of the 1 m -suppressed dimension-five operators in the static effective field theory lagrangian have been calculated to one loop order, where the matrix element of the time component of the axial vector current determines the decay constants of pseudoscalar heavy-light mesons.
TL;DR: In this article, the authors discuss semileptonic decays of heavy mesons into light pseudoscalar and vector mesons and exploit the symmetries arising in the heavy quark limit.
Abstract: We discuss semileptonic decays of heavy mesons into light pseudoscalar and vector mesons. Exploiting the symmetries arising in the heavy quark limit we use the known data on semileptonicD decays to predict the corresponding rates for semileptonicB decays. These consideration may serve as a model independent way to extract theub matrix element of the CKM matrix.
TL;DR: In this article, the critical behavior of a strongly coupled three dimensional abelian gauge theory with N flavors and fermion self interactions is studied, and the region in coupling constant space in which a Chern-Simons term is dynamically generated is determined.
TL;DR: In this article, it was shown that the approximate constancy of the quantity δm2 = mv2−mv2, among vector and pseudoscalar mesons (Q q ) is valid in the infinite mass limit that has been proposed recently.
TL;DR: In this paper, a Bethe-Salpeter (BS) approach to the minimal dynamical symmetry breaking model where the electroweak symmetry is broken by a condensate of top quarks is discussed.
TL;DR: In this paper, a model independent analysis of possibilities of looking for new gauge bosons in radiative decays of π0, η and η′ mesons was performed.
Abstract: We perform the model independent analysis of possibilities of looking for new gauge bosons in radiative decays of π0, η, η′ mesons. For this purpose we consider various experimental constraints on properties of light gauge bosons. It is shown that the branching ratios of these decays can be as large as: BR(π0→γ+X)≲10−3, BR(η→γ+X)≲10−4, BR(η′→γ+X)≲10−6, what is highly interesting from the experimental point of view.
01 Oct 1991
TL;DR: In this article, a lattice study of electromagnetic decays of vector mesons V into pseudoscalar mesons P, relevant to radiative and conversion decays V→Pl + l -.
Abstract: We present a lattice study of electromagnetic decays of vector mesons V into pseudoscalar mesons P, relevant to radiative decays V→Pγ and conversion decays V→Pl + l - . The form factor ƒ q (q 2 ) , associated with the electromagnetic current of the quark q, has been computed using Wilson fermions in the quenched approximation. The computations have been performed by averaging the results over 15 gauge configurations, generated by the Metropolis algorithm, at β =6.0, on a 20×10 2 ×40 lattice. By extrapolating linearly the form factor to q 2 =0, we have obtained ƒ u (0)=2.2±0.3 GeV −1 for a massless quark and ƒ s (0)=1.8±0.2 GeV −1 for a strange quark, in remarkable agreement with the experimental values, ƒ u (0)+2.32±0.08 GeV −1 and ƒ s (0)= 1.84±0.06 GeV −1 . A larger value of ƒ u (0) is obtained from the vector meson dominance model. We have also estimated the partial widths for the conversion decays using both a linear dependence on q 2 of the form factor and the vector meson dominance predictions.