Showing papers on "Pseudoscalar published in 1993"
TL;DR: The search for light scalar and/or pseudoscalar particles that couple to two photons by studying the propagation of a laser beam through a transverse magnetic field finds that the coupling is high.
Abstract: We have searched for light scalar and/or pseudoscalar particles that couple to two photons by studying the propagation of a laser beam ($\ensuremath{\lambda}=514$ nm) through a transverse magnetic field A limit of 35\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}10}$ rad was set on a possible optical rotation of the beam polarization for an effective path length of 22 km in a 325 T magnetic field We find that the coupling ${g}_{\ensuremath{\alpha}\ensuremath{\gamma}\ensuremath{\gamma}}l36\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ Ge${\mathrm{V}}^{\ensuremath{-}1}$ at the 95% confidence level, provided ${m}_{a}l{10}^{\ensuremath{-}3}$ eV Similar limits can be set from the absence of ellipticity in the transmitted beam We also searched for photon regeneration in a magnetic field and found the limit ${g}_{\ensuremath{\alpha}\ensuremath{\gamma}\ensuremath{\gamma}}l67\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ Ge${\mathrm{V}}^{\ensuremath{-}1}$ for the same range of particle mass
310 citations
TL;DR: In this paper, the authors derived the low-energy effective action of an extended Nambu-Jona-Lasinio (ENJL) model to O(p4) in the chiral counting.
162 citations
TL;DR: In this article, the weak interactions of pseudoscalar mesons with meson resonances with spin 0, 1 to lowest order in the derivative expansion were considered and the resonance contributions to the O( p 4 ) weak coupling constants were determined.
122 citations
TL;DR: In this paper, the authors present the QCD corrections to the gluon fusion processes of the scalar Higgs particles h, H, and the pseudoscalar higgs particle A in the minimal supersymmetric extension of the Standard Model, which are in general large and positive, increasing the production cross section up to factors of about 2.
121 citations
TL;DR: In this article, the radiative corrections to the 3 × 3 scalar and the 2 × 2 pseudoscalar neutral Higgs boson mass matrices are calculated in the supersymmetric extension of the standard model including a gauge singlet superfield in the effective potential approach.
118 citations
TL;DR: The Bethe-Salpeter equation is solved in order to calculate the spectrum of pseudoscalar, vector, and scalar meson bound states for light as well as heavy quarks and obeys known relations derived on the basis of current algebra for light quark and a nonrelativistic analysis for heavy quark.
Abstract: We solve the Bethe-Salpeter equation in order to calculate the spectrum of pseudoscalar, vector, and scalar meson bound states for light as well as heavy quarks, extending our previous calculation of pseudoscalar mesons. The fermion propagators appearing in the equation are obtained by solving the Schwinger-Dyson equation consistently with the Bethe-Salpeter equation, a procedure necessary for demonstrating the Goldstone nature of the pion in the chiral limit. We probe in our calculations a model for the gluon propagator which leads to the expected three-dimensional potential in configuration space, while maintaining its known ultraviolet behavior. Our procedure provides a unified description of both the light and heavy mesons and obeys known relations derived on the basis of current algebra for light quarks and a nonrelativistic analysis for heavy quarks. The results are in good agreement with experiment for the mass spectrum and for the pseudoscalar mesons' decay constants. We also calculate electromagnetic and isospin mass splittings for these mesons.
105 citations
TL;DR: In this paper, the radiative corrections to the $3\times3$scalar and the pseudoscalar neutral Higgs boson mass matrices are calculated in the supersymmetric extension of the standard model including a gauge singlet superfield in the effective potential approach.
Abstract: The radiative corrections to the $3\times3$scalar and the $2\times2$ pseudoscalar neutral Higgs boson massmatrices are calculated in the supersymmetric extension of the standard model including a gauge singlet superfield in the effective potential approach. The full $t$ and $b$ quark/squark contributions including the nonlogarithmic terms are taken into account, which are seen to affect the result significantly. An analytic formula for the upper bound on the mass of the lightest neutral Higgs scalar including these corrections is given. (Figure available upon request)
101 citations
01 Jan 1993
TL;DR: In this paper, the authors presented the QCD corrections to the gluon fusion processes of the scalar Higgs particles h, H, H and A in the minimal supersymmetric extension of the Standard Model.
Abstract: We present the QCD corrections to the gluon fusion processes of the scalar Higgs particles h, H and the pseudoscalar Higgs particle A in the minimal supersymmetric extension of the Standard Model. These corrections are in general large and positive, increasing the production cross section up to factors of about 2. While they depend only weakly on the Higgs masses, they are strongly dependent on the parameter tg ft.
98 citations
TL;DR: The cross section for the electromagnetic production of different particles in heavy-ion collision is derived within the external field approach and the impact-parameter dependent production of scalar and pseudoscalar bosons, charged (spin 0) boson pairs, and fermion pairs is discussed.
Abstract: The cross section for the electromagnetic production of different particles in heavy-ion collision is derived within the external field approach. Introducing polarized photon-fusion cross sections, it is possible to generalize the equivalent photon method to describe the impact-parameter dependence of the particle production. The impact-parameter dependent production of scalar and pseudoscalar (spin 0) bosons, charged (spin 0) boson pairs, and fermion pairs is discussed.
94 citations
CERN1
TL;DR: In this paper, a sum rule relating the first moment of the photon structure function g 1 γ to the three-current AVV correlation functions involving the strong and electromagnetic U(1) anomalies is presented.
46 citations
TL;DR: In this article, the branching ratios of the tau decays into three mesons were computed by first using the structure of the chiral currents and that of the Wess-Zumino anomaly and finally implementing all possible low-lying resonances in the different channels.
Abstract: In this paper we compute the branching ratios of the tau decays into three mesons. The hadronic matrix elements are obtained by first using the structure of the chiral currents and that of the Wess-Zumino anomaly and finally implementing all possible low-lying resonances in the different channels.
TL;DR: In this paper, the authors examined the muon capture process from two points of view: the elementary particle model (EPM) and the impulse approximation (IA), where the new wave functions allow extremely accurate evaluations of the nuclear matrix elements, in a microscopic way.
TL;DR: In this article, the light hadron spectrum and decay constants for quenched QCD at β = 6.2 were compared with those obtained using the standard Wilson fermion action on the same set of 18 gauge configurations.
TL;DR: In this article, the authors derived vector, axial-vector, scalar and pseudoscalar two-point functions at low and intermediate energies and showed that the similarity between the shape of the experimentally known spectral functions and the ones they derived, is greatly improved with respect to those predicted by the usual constituent quark like models.
Abstract: We discuss vector, axial-vector, scalar and pseudoscalar two-point functions at low and intermediate energies. We first review what is known from chiral perturbation theory, as well as from a heat kernel expansion within the context of the extended Nambu-Jona-Lasinio (ENJL) model of ref. \cite{12}. In this work we derive then these two-point functions to all orders in the momenta and to leading order in $1/N_c$. We find an improved high-energy behaviour and a general way of parametrizing them that shows relations between some of the two-point functions, which are also valid in the presence of gluonic interactions. The similarity between the shape of the experimentally known spectral functions and the ones we derive, is greatly improved with respect to those predicted by the usual constituent quark like models. We also obtain the scalar mass $M_S = 2 M_Q$ independent of the regularization scheme. In the end, we calculate fully an example of a nonleptonic matrix element in the ENJL--model, the $\pi^+-\pi^0$ electromagnetic mass difference and find good agreement with the measured value.
TL;DR: In this article, the authors compared the Bethe-Salpeter amplitudes for the pion, rho, and nucleon calculated in quenched lattice QCD with the MIT bag model.
TL;DR: In this article, the authors investigate a potentially large CP violating asymmetry in the neutral Higgs boson decay into a heavy quark pair or a $W+$--$W^-$ pair.
Abstract: We investigate a potentially large CP violating asymmetry in the neutral Higgs boson decay into a heavy quark pair or a $W^+$--$W^-$ pair. The source of the CP nonconservation is in the Yukawa couplings of the Higgs boson which can contain both scalar and pseudoscalar pieces. One of the interesting consequence is the different rates of the Higgs boson decays into CP conjugate polarized states. The required final state interactions can be either the strong or the electroweak interactions. The CP violating asymmetry can manifests itself in the asymmetry in the energies of the secondary decay products of these heavy quarks and $W$ bosons. Such asymmetry can be measureable in the future colliders such as SSC or LHC.
TL;DR: In this article, the authors extend the analysis to the anomalous sector of chiral lagrangians by comparing the conventional vector model, the hidden gauge symmetry model, where vectors are gauge bosons of a spontaneously broken gauge symmetry, and the model where they are introduced through a tensor field.
TL;DR: In this article, the authors considered two mechanisms of pseudoscalar field mixing (mass-mixing and current mixing) and derived the values of η−η′ −mixing angle θ p ≥ 0.
Abstract: Proceeding from the expansion of composite operators in interpolating hadronic fields, the width of the decays η(η′)→γγ andJ/ψ→η(η′)γ have been calculated. Two mechanisms of pseudoscalar field mixing (“mass-mixing” and “current-mixing”) are considered. In the given schemes, the values of η−η′-mixing angle θ
p
are, respectively, (−15.0±1.8)o and (−19.7±2.2)o.
TL;DR: Within the ladder approximation, the general form of the quark-antiquark interaction kernel, consistent with chiral symmetry, is investigated through the combined use of Ward identities for the axial and vector currents.
Abstract: Within the ladder approximation, the general form of the quark-antiquark interaction kernel, consistent with chiral symmetry, is investigated through the combined use of Ward identities for the axial and vector currents. In the charm and bottom sectors we show that chiral symmetry still plays an important role, through the functional form of the quark-antiquark forces. To maintain the chiral symmetry the scalar, pseudoscalar and tensor terms of the local interaction kernel must appear in a combination consistent with the equation Ks = Kp = 3Kt. Within the validity domain of the ladder approximation, this result is independent of the quark current masses. While the vector and axial parts, Kv and Ka, are not constrained by chiral symmetry, they are needed in order to implement spontaneous chiral-symmetry breaking, since the above terms alone would not do. In addition to the usual spin-spin, spin-orbit and tensor interactions, the existence of a Lorentz-tensor term in the kernel gives rise to a second tensor force which does not appear in previous studies of mesonic spectroscopy.
TL;DR: In this article, the quarks are coupled to the pseudoscalar mesons π, K, η and the couplings reflect chiral symmetry breaking, and it is shown that the physical effects of operators involving (i γ ·D−m q ) are not zero.
TL;DR: In this paper, a general treatment of SU(3) breaking of the charm decay hamiltonian by an octet leads to an unpractically large number of new representations.
TL;DR: It is found that [ital s]-channel resonance formation and quark-exchange processes are sufficient to reproduce experimental observations, and that the new predictions are qualitatively consistent with the earlier results.
Abstract: We discuss the relative importance of several possible hadron-hadron interaction mechanisms and review a coupled-channel Schr\"odinger model incorporating some of these mechanisms. Its application to pseudoscalar-pseudoscalar $S$-wave scattering is reviewed and updated to include new insights about the underlying intermeson interactions. We find that $s$-channel resonance formation and quark-exchange processes are sufficient to reproduce experimental observations, and that the new predictions are qualitatively consistent with the earlier results. New results for exotic ${K}^{+}{K}^{+}$ scattering are also presented and compared with a Born-level quark-exchange calculation.
TL;DR: In this article, ground-state scalar isoscalar mesons and a scalar glueball are described in a U(3) × U( 3) chiral quark model of the Nambu-Jona-Lasinio (NJL) type with the Hooft interaction.
TL;DR: Using both scalar and scalar plus pseudoscalar confinement, the spectra of charmonium, [ital b]-quarkonium, and the light mesons are obtained with scalar linear confinement in the instantaneous approximation to the Bethe-Salpeter equation.
Abstract: Singular integral equations for quarkonium ([ital q[bar q]]) spectra are solved in momentum space for relativistic confinement plus Coulomb potentials including spin. The confinement potential in momentum space is defined using an analytical regularization scheme. Further manipulations give rise to integro-differential equations and we obtain analytical approximations for the remaining singular integrals. The procedure is tested with two different reductions of the Bethe-Salpeter equation. Using both scalar and scalar plus pseudoscalar confinement we obtain the spectra of charmonium, [ital b]-quarkonium, and the light mesons. We compare the results with experiment and with results obtained by other techniques. Eigenfunctions for selected eigenstates are presented. A good description of both the light and heavy mesons is then obtained with scalar linear confinement in the instantaneous approximation to the Bethe-Salpeter equation. This description is based upon the inclusion of a Breit term to approximate transverse gluon effects.
TL;DR: In an expansion in inverse powers of the heavy-quark mass, it is found that all zeroth- and first-order heavy- quark symmetry relations are satisfied and the main results are the following.
Abstract: A simple relativistic model of heavy-quark--light-quark mesons is proposed. In an expansion in inverse powers of the heavy-quark mass we find that all zeroth- and first-order heavy-quark symmetry relations are satisfied. The main results are the following. The difference between the meson mass and the heavy-quark mass plays a significant role even at zeroth order. The slope of the Isgur-Wise function at the zero recoil point is typically less than [minus]1. The first-order correction to the pseudoscalar decay constant is large and negative. The four universal functions describing the first-order corrections to the semileptonic decay form factors are small. These latter corrections are quite insensitive to the choice of model parameters, and in particular to the effects of hyperfine mass splitting.
TL;DR: In this article, a high statistics study of the leptonic decay constant of heavy pseudoscalar mesons using propagating heavy Wilson quarks within the quenched approximation, on lattices covering sizes from about 0.7~fm to 2~fm.
Abstract: We present a high statistics study of the leptonic decay constant $f_P$ of heavy pseudoscalar mesons using propagating heavy Wilson quarks within the quenched approximation, on lattices covering sizes from about 0.7~fm to 2~fm. Varying $\beta$ between 5.74 and 6.26 we observe a sizeable $a$ dependence of $f_P$ when one uses the quark field normalization that was suggested by Kronfeld and Mackenzie, compared with the weaker dependence observed for the standard relativistic norm. The two schemes come into agreement when one extrapolates to $a \rightarrow 0$. The extrapolations needed to reach the continuum quantity $f_B$ introduce large errors and lead to the value $f_B=0.18(5)$~GeV in the quenched approximation. This suggests that much more effort will be needed to obtain an accurate lattice prediction for $f_B$.
TL;DR: The total effective low energy lagrangian for K → π + pseudoscalar decays has been derived for any model involving light elementary pseudooscalars.
TL;DR: The correction required to convert a lattice calculation of the pseudoscalar heavy-light meson decay constant into a value appropriate for the continuum is given.
Abstract: We calculate the [ital O]([alpha][sub [ital s]]) corrections to bilinear lattice vertex operators in nonrelativistic QCD (NRQCD) on the lattice. We use the lowest-order (in 1/[ital M]) NRQCD action which includes the time derivative and kinetic energy terms, but we ignore spin effects. We give the correction required to convert a lattice calculation of the pseudoscalar heavy-light meson decay constant into a value appropriate for the continuum. For the light fermion we have used ordinary Wilson fermions, improved Wilson fermions, and naive fermions. We also give the correction required for a calculation of the vector heavy-heavy meson leptonic width. This is unfortunately large.
TL;DR: In this paper, a model for a bound quark-antiquark system is constructed from quark spinor equations and the associated pseudoscalar massless interaction potential equations in a way departing from conventional relativistic quantum mechanics.
Abstract: A model for a bound quark-antiquark system is constructed from quark spinor equations and the associated pseudoscalar massless interaction potential equations in a way departing from conventional relativistic quantum mechanics. From the so-constructed covariant meson equations, linear confinement arises naturally. Nonlinear radial equations for the pseudoscalar and vector mesons in the rest frame are derived without approximation. An internal complex space is introduced for representation of the quark flavors. Quark masses are generalized to operators operating on functions in this space. A simple model is proposed for the meson internal functions and mass operators producing the squares of the average quark masses as eigenvalues. The present space-time model calls for a particle classification scheme different from the usual nonrelativistic one. When combined with the internal model, it may account for the gross structure of the meson spectra together with the form of an empirical relation. Upper limits of bare quark masses are estimated from simplified analytical solutions of the radial equations and agree approximately with the bare quark masses obtained from baryon data in a companion paper. The radial equations are solved numerically yielding estimates of the strong interaction radii of the ground state mesons.
TL;DR: In this article, the authors present a general scheme for extracting effective degrees of freedom from an underlying fundamental Lagrangian, through a series of well-defined transformations in the functional integral of the cut-off theory.
Abstract: We present a general scheme for extracting effective degrees of freedom from an underlying fundamental Lagrangian, through a series of well-defined transformations in the functional integral of the cut-off theory. This is done by introducing collective fields in a gauge-symmetric manner. Through appropriate gauge fixings of this symmetry one can remove long-distance degrees of freedom from the underlying theory, replacing them by the collective fields. Applying this technique to QCD, we set out to extract the long-distance dynamics in the pseudoscalar flavour singlet sector through a gauging (and subsequent gauge fixing) of the $U(1)_A$ flavour symmetry which is broken by the anomaly. By this series of exact transformations of a cut-off generating functional for QCD, we arrive at a theory describing the long-distance physics of a pseudoscalar flavour singlet meson coupled to the residual quark-gluon degrees of freedom. As examples of how known low-energy physics can be reproduced in this formulation, we rederive the Witten-Veneziano relation between the $\eta'$ mass and the topological susceptibility, now for any value of the number of colours $N_c$.