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Showing papers on "Meson published in 1998"


Journal ArticleDOI
TL;DR: In this article, a new eta-eta' mixing scheme is proposed, where all basic parameters are fixed to first order of flavor symmetry breaking and a mass matrix, quadratic in the masses, with specified elements.
Abstract: We propose a new eta-eta' mixing scheme where we start from the quark flavor basis and assume that the decay constants in that basis follow the pattern of particle state mixing. On exploiting the divergences of the axial vector currents - which embody the axial vector anomaly - all basic parameters are fixed to first order of flavor symmetry breaking. That approach naturally leads to a mass matrix, quadratic in the masses, with specified elements. We also test our mixing scheme against experiment and determine corrections to the first order values of the basic parameters from phenomenology. Finally, we generalize the mixing scheme to include the eta(c). Again the divergences of the axial vector currents fix the mass matrix and, hence, mixing angles and the charm content of the eta and eta'.

539 citations


Journal ArticleDOI
J. Gronberg1, T. S. Hill1, R. Kutschke1, Dj Lange1  +221 moreInstitutions (27)
TL;DR: Using the CLEO II detector, the authors measured the differential cross sections for exclusive two-photon production of light pseudoscalar mesons {pi}{sup 0, {eta, and {eta}{prime}.
Abstract: Using the CLEO II detector, we have measured the differential cross sections for exclusive two-photon production of light pseudoscalar mesons {pi}{sup 0}, {eta}, and {eta}{prime}. From our measurements we have obtained the form factors associated with the electromagnetic transitions {gamma}*{gamma} {yields} meson. We have measured these form factors in the momentum transfer ranges from 1.5 to 9, 20, and 30 GeV2 for {pi}{sup 0}, {eta}, and {eta}{prime}, respectively, and have made comparisons to various theoretical predictions.

396 citations


Journal ArticleDOI
TL;DR: In this paper, a systematic study of twist 3 light-cone distribution amplitudes of vector mesons in QCD is presented, which is based on conformal expansion and takes into account meson and quark mass corrections.

363 citations


Journal ArticleDOI
Patricia Ball1, Vladimir M. Braun
TL;DR: In this article, the first complete results for the semileptonic and rare radiative form factors of the $B$ meson's weak decay into a light vector meson were presented.
Abstract: We present the first complete results for the semileptonic and rare radiative form factors of the $B$ meson's weak decay into a light vector meson $(\ensuremath{\rho},\ensuremath{\omega}{,K}^{*},\ensuremath{\varphi})$ in the light-cone sum rule approach. The calculation includes radiative corrections, higher twist corrections, and SU(3) breaking effects. The theoretical uncertainty is investigated in detail. A simple parametrization of the form factors is given in terms of three parameters each. We find that the form factors observe several relations inspired by heavy quark symmetry.

329 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented a systematic study of twist three light-cone distribution amplitudes of vector mesons in QCD, which is based on conformal expansion and takes into account meson and quark mass corrections.
Abstract: We present a systematic study of twist three light-cone distribution amplitudes of vector mesons in QCD, which is based on conformal expansion and takes into account meson and quark mass corrections. A complete set of distribution amplitudes is constructed for rho, omega, K* and phi mesons, which satisfies all (exact) equations of motion and constraints from conformal expansion. Nonperturbative input parameters are calculated from QCD sum rules, including an update of SU(3) breaking corrections in the leading twist distributions.

266 citations


Journal ArticleDOI
Patricia Ball1
TL;DR: In this article, the form factors describing semileptonic and penguin-induced decays of B mesons into light pseudoscalar mesons were calculated from QCD sum rules on the light-cone including contributions up to twist 4, radiative corrections to the leading twist contribution and SU(3)-breaking effects.
Abstract: I calculate the form factors describing semileptonic and penguin-induced decays of B mesons into light pseudoscalar mesons. The form factors are calculated from QCD sum rules on the light-cone including contributions up to twist 4, radiative corrections to the leading twist contribution and SU(3)-breaking effects. The theoretical uncertainty is estimated to be \sim 15%. The heavy-quark-limit relations between semileptonic and penguin form factors are found to be valid in the full accessible range of momentum transfer.

227 citations


Journal ArticleDOI
R. Barate1, D. Buskulic1, D. Decamp1, Philippe Ghez1  +410 moreInstitutions (33)
TL;DR: In this article, the ALEPH detector at LEP1 has been used for detailed studies of both perturbative and non-perturbative aspects of strong interactions to be carried out using hadronic Z and tau decays.

224 citations


Journal ArticleDOI
TL;DR: In this paper, the masses and decay widths of the gluonia using QCD spectral sum rules and low energy theorems were derived for the scalar and tensor sectors.

209 citations


Journal ArticleDOI
TL;DR: In this paper, a measurement of low-mass electron pairs observed in 158 GeV/nucleon Pb-Au collisions is reported, where the pair yield integrated over the range of invariant masses 0.2 ≤ m ≤ 2.0 GeV 2 is enhanced by a factor of 3.5 ± 0.4 (stat) ± 1.9 (syst) over the expectation from neutral meson decays.

199 citations


Journal ArticleDOI
TL;DR: In this paper, the mass spectrum of orbitally and radially excited states of $B$ and $D$ mesons is calculated in the framework of the relativistic quark model and the expansion in inverse powers of the heavy quark mass is carried out up to first order.
Abstract: The mass spectrum of orbitally and radially excited states of $B$ and $D$ mesons is calculated in the framework of the relativistic quark model. The expansion in inverse powers of the heavy quark mass is carried out up to first order, while the light quark is treated without expansion. We find that the relativistic treatment of the light quark plays an important role. Different patterns of $P$ level inversion are discussed. The obtained masses of orbitally and radially excited states are in accord with available experimental data and heavy quark symmetry relations.

187 citations


Journal ArticleDOI
TL;DR: In this paper, the authors have added some some refrences and given some figures giving results in parameter space allowed by b \to s \gamma, and more or less remains unchanged.
Abstract: We have added some some refrences & given some figures giving results in parameter space allowed by b \to s \gamma. Conclusions more or less remains unchanged.

Journal ArticleDOI
TL;DR: In this paper, the two-pion exchange diagrams with single and double delta-isobar excitation contributing to elastic NN-scattering were evaluated, within one-loop chiral perturbation theory, and they were shown to produce the correct amount of isoscalar central attraction as needed in the peripheral partial waves with L ⩾ 3.

Journal ArticleDOI
TL;DR: The Crystal Barrel experiment at the Low Energy Antiproton Ring (LEAR) at CERN as discussed by the authors collected very large statistical samples in pbarp annihilation, especially at rest and with emphasis on final states with high neutral multiplicity.
Abstract: This report reviews the achievements of the Crystal Barrel experiment at the Low Energy Antiproton Ring (LEAR) at CERN. During seven years of operation Crystal Barrel has collected very large statistical samples in pbarp annihilation, especially at rest and with emphasis on final states with high neutral multiplicity. The measured rates for annihilation into various two-body channels and for electromagnetic processes have been used to test simple models for the annihilation mechanism based on the quark internal structure of hadrons. From three-body annihilations three scalar mesons, a0(1450), f0(1370) and f0(1500) have been established in various decay modes. One of them, f0(1500), may be identified with the expected ground state scalar glueball.

Journal ArticleDOI
TL;DR: In this article, the two-pion exchange diagrams with single and double delta-isobar excitation contributing to elastic NN-scattering were evaluated within one-loop chiral perturbation theory.
Abstract: We evaluate, within one-loop chiral perturbation theory, the two-pion exchange diagrams with single and double delta-isobar excitation contributing to elastic NN-scattering. We find that virtual $\Delta$-excitation processes (in the static limit) produce the correct amount of isoscalar central attraction as needed in the peripheral partial waves with $L\geq 3$. Furthermore we compute the two-loop diagrams involving the $\pi\pi$-interaction (so-called correlated $2\pi$-exchange). Contrary to common believe these processes lead to negligibly small and repulsive corrections to the NN-potential. The exchange of vector mesons ($\rho, \omega$) turns out to be important for the F-wave phase shifts above $T_{lab}=150$ MeV. Without adjustable parameters we are able to reproduce the empirical NN phase shifts up to 350 MeV for $L\geq 3$ and up to about (50--80) MeV for the D-waves. This is therefore the characteristic window in which the NN-interaction is basically governed by chiral symmetry. Not surprisingly, the lower partial waves require non-perturbative methods and additional short-distance parametrizations of the NN-dynamics.

Journal ArticleDOI
TL;DR: In this article, a simple parametrization of Breit-Wigner type for the hadronic side of the QCD sum rule for ϱ mesons in vacuum as well as in a nuclear medium was explored.

23 Jul 1998
TL;DR: In this paper, the Drell-Yan cross section ratios, s(p+d)/s(p + p+p) for the proton over the range 0.02 < x < 0.345, and the relationship between the E866 results and the NMC measurements of the Gottfried integral is discussed.
Abstract: The Drell-Yan cross section ratios, s(p+d)/s(p+p), measured in Fermilab E866, have led to the first determination of d(x)/u(x), d(x)-(x), and the integral of d(x)-u(x) for the proton over the range 0.02 < x < 0.345. The E866 results are compared with predictions based on parton distribution functions and various theoretical models. The relationship between the E866 results and the NMC measurements of the Gottfried integral is discussed. The agreement between the E866 results and models employing virtual mesons indicates these non-perturbative processes play an important role in the origin of the d, u asymmetry in the nucleon sea.

Journal ArticleDOI
TL;DR: In this article, a generalized Lagrangian for the description of hadronic matter based on the linear ϵ-Lagrangian model is proposed. But it is not shown that the Lagrangians of the baryon octet and the spin-0 and spin-1 nonets are invariant to broken scale invariance.
Abstract: A generalized Lagrangian for the description of hadronic matter based on the linear $\mathrm{SU}{(3)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}{(3)}_{R}$ $\ensuremath{\sigma}$ model is proposed. Besides the baryon octet, the spin-0 and spin-1 nonets, a gluon condensate associated with broken scale invariance is incorporated. The observed values for the vacuum masses of the baryons and mesons are reproduced. In mean-field approximation, vector and scalar interactions yield a saturating nuclear equation of state. We discuss the difficulties and possibilities to construct a chiral invariant baryon-meson interaction that leads to a realistic equation of state. It is found that a coupling of the strange condensate to nucleons is needed to describe the hyperon potentials correctly. The effective baryon masses and the appearance of an abnormal phase of nearly massless nucleons at high densities are examined. A nonlinear realization of chiral symmetry is considered, to retain a Yukawa-type baryon-meson interaction and to establish a connection to the Walecka model.


Journal ArticleDOI
TL;DR: In this paper, twist-two quark interference fragmentation functions in helicity density matrix formalism were introduced and their physical implications were studied, showing how the nucleon's transversity distribution can be probed through the final state interaction between two mesons produced in the current fragmentation region in deep inelastic scattering.
Abstract: We introduce twist-two quark interference fragmentation functions in helicity density matrix formalism and study their physical implications. We show how the nucleon's transversity distribution can be probed through the final state interaction between two mesons ($\pi^+\pi^-$, $K\bar K$, or $\pi K$) produced in the current fragmentation region in deep inelastic scattering on a transversely polarized nucleon.

Journal ArticleDOI
TL;DR: In this article, the authors presented new Sigma beam asymmetry data for eta meson photoproduction on the proton, using a novel tagged, laser backscattered, linearly polarized photon beam up to 1.1 GeV.
Abstract: We present new Sigma beam asymmetry data for eta meson photoproduction on the proton, using a novel tagged, laser backscattered, linearly polarized photon beam up to 1.1 GeV. The data show large, positive asymmetries, at all incident photon energies. In addition to the S-11(1535) and D-13(1520) resonances necessary to reproduce the cross sections, P-13(1720) and D-15(1675) "four stars" resonances contribute to the Sigma observable, but cannot reproduce the strong forward asymmetries measured at energies higher than 900 MeV.

Journal ArticleDOI
TL;DR: In this article, a general survey of photon-photon luminosities in relativistic heavy ion collisions is discussed, and the effects of strong interactions and nuclear size are taken into account.
Abstract: In central collisions at relativistic heavy ion colliders such as the Relativistic Heavy Ion Collider (RHIC), Brookhaven and the Large Hadron Collider (LHC) (in its heavy ion mode) at CERN, Geneva, one aims at detecting a new form of hadronic matter - the quark gluon plasma. It is the purpose of this review to discuss a complementary aspect of these collisions, the very peripheral ones. Owing to coherence, there are strong electromagnetic fields of short duration in such collisions. They give rise to photon-photon and photon-nucleus collisions with high flux up to an invariant mass region hitherto unexplored experimentally. After a general survey photon-photon luminosities in relativistic heavy ion collisions are discussed. Special care is taken to include the effects of strong interactions and nuclear size. Then photon-photon physics at various -invariant mass scales is discussed. The region of several GeV, relevant for RHIC is dominated by quantum chronodynamics phenomena (meson and vector meson pair production). Invariant masses of up to about 100 GeV can be reached at LHC, and the potential for new physics is discussed. Photonuclear reactions and other important background effects, especially diffractive processes are also discussed. A special chapter is devoted to lepton-pair production, especially electron-positron pair production; owing to the strong fields new phenomena, especially multiple pair production, will occur there.

Journal ArticleDOI
TL;DR: In this paper, the authors calculate the cross sections for dissociation of pions and φ mesons under the framework of a meson exchange model and find that these cross sections are small at center-of-mass energies less than 1 GeV above threshold, and that dissociation rates are less than $0.01\mathrm{fm}/c$ in a thermal meson gas at temperatures where such a description makes sense.
Abstract: We calculate the cross sections for dissociation of $J/\ensuremath{\psi}$ by pions and \ensuremath{\rho} mesons within the framework of a meson exchange model. We find that these cross sections are small at center-of-mass energies less than 1 GeV above threshold, and that dissociation rates are less than $0.01\mathrm{fm}/c$ in a thermal meson gas at temperatures where such a description makes sense.

Journal ArticleDOI
TL;DR: In this article, a model independent prediction for the slope parameter of the decay rate into helicity zero D1 at zero recoil is given, including ΛQCD/mQ corrections with some model dependence away from zero recoil.
Abstract: Exclusive semileptonic B decays into excited charmed mesons are investigated at order ΛQCD/mQ in the heavy quark effective theory. Differential decay rates for each helicity state of the four lightest excited D mesons (D1, D2*, D0*, and D1*) are examined. At zero recoil, ΛQCD/mQ corrections to the matrix elements of the weak currents can be written in terms of the leading Isgur-Wise functions for the corresponding transition and meson mass splittings. A model independent prediction is found for the slope parameter of the decay rate into helicity zero D1 at zero recoil. The differential decay rates are predicted, including ΛQCD/mQ corrections with some model dependence away from zero recoil and including order αs corrections. Ratios of various exclusive branching ratios are computed. Matrix elements of the weak currents between B mesons and other excited charmed mesons are discussed at zero recoil to order ΛQCD/mQ. These amplitudes vanish at leading order, and can be written at order ΛQCD/mQ in terms of local matrix elements. Applications to B decay sum rules and factorization are presented.

Journal ArticleDOI
TL;DR: In this article, the quark-meson coupling (QMC) model is applied to a systematic study of Λ, Σ and Ξ hypernuclei, and the model automatically leads to a very weak spin-orbit interaction for the Λ in a hyper-nucleus.

Journal ArticleDOI
TL;DR: In this article, a general formulation for constructing covariant helicity-coupling amplitudes involving two-body decays with arbitrary integer spins is given, and the decay amplitudes are given exclusively in terms of both definite orbital angular momentum and total intrinsic spin.
Abstract: A general formulation is given for constructing covariant helicity-coupling amplitudes involving two-body decays with arbitrary integer spins. The decay amplitudes are given exclusively in terms of both definite orbital angular momentum and total intrinsic spin. A systematic method is developed for calculating the energy and momentum dependence of daughter particles in the decay amplitudes, and a general formula for arbitrary integer spins is given. A number of illustrative examples is worked out, among which is that of the Higgs boson decay into two gauge bosons.

Journal ArticleDOI
TL;DR: In this paper, the in-medium K and K spectra of the φ meson were determined from a coupled channel approach based on a chiral effective Lagrangian.

Journal ArticleDOI
TL;DR: In this paper, the Hartree-Fock (HF) equations were derived and applications to infinite matter and finite nuclei were discussed using a generalized Slater approximation for the density matrix.
Abstract: The density matrix expansion is used to obtain a local energy density functional for interactions with a realistic meson exchange structure. Hartree-Fock (HF) equations are derived and applications to infinite matter and finite nuclei are discussed. Using a generalized Slater approximation for the density matrix the HF equations still incorporate the momentum structure of the underlying finite range interaction. For applications a density dependent effective interaction is determined from a $G$ matrix where the density dependence is adjusted to the saturation properties of symmetric nuclear matter. Intending applications to systems far off stability special attention is paid to the low density regime and asymmetric nuclear matter. Results are compared to Skyrme HF calculations. The ground state properties of stable nuclei are well reproduced. The potential of the approach is further exemplified in calculations for $A=100\ensuremath{-}140$ tin isotopes. Extended neutron skins are found beyond ${}^{130}\mathrm{Sn}$ corresponding to solid layers of neutron matter surrounding a core of normal composition.

Posted Content
TL;DR: The Gross-Neveu Model as mentioned in this paper is a well-known model for counting rules for correlation functions and is used in N-Counting Rules for Baryons 5.1 Consistency Conditions 6.2 1/N Corrections 6.3 Solution of consistency conditions 6.6 Axial U(1) and the eta' Mass 4.4 Meson Phenomenology 4.3 Chiral Perturbation Theory 4.5 Non-leptonic K Decay 4.7 Resonances and 1/n
Abstract: 1. Introduction 2. The Gross-Neveu Model 3. QCD 3.1 N-Counting Rules for Diagrams 3.1.1 U(1) Ghosts 3.2 The 't Hooft Model 3.3 $N$-Counting Rules for Correlation Functions 3.4 The Master Field 4. Meson Phenomenology 4.1 Zweig's Rule 4.2 Exotics 4.3 Chiral Perturbation Theory 4.4 Non-leptonic K Decay 4.5 $K-\bar K$ mixing 4.6 Axial U(1) and the eta' Mass 4.7 Resonances and 1/N 5 Baryons 5.1 N-Counting Rules for Baryons 5.2 The Non-Relativistic Quark Model 6 Spin-Flavor Symmetry for Baryons 6.1 Consistency Conditions 6.2 1/N Corrections 6.3 Solution of Consistency Conditions 7 Masses with SU(3) Breaking 8 Other Results for Baryons 9 Large N and Chiral Perturbation Theory

Journal ArticleDOI
TL;DR: In this paper, the authors investigated theoretically whether it is feasible to detect η - and ω -nucleus bound states in closed shell nuclei, 16 O, 40 Ca, 90 Zr and 208 Pb.

Journal ArticleDOI
TL;DR: In this article, the performance of some recent potential models suggested as effective interactions between constituent quarks was investigated and it was shown that these models fail in describing the $N$ and $\ensuremath{\Delta}$ spectra.
Abstract: We study the performance of some recent potential models suggested as effective interactions between constituent quarks. In particular, we address constituent quark models for baryons with hybrid $Q\ensuremath{-}Q$ interactions stemming from one-gluon plus meson exchanges. Upon recalculating two of such models we find them to fail in describing the $N$ and $\ensuremath{\Delta}$ spectra. Our calculations are based on accurate solutions of the three-quark systems in both a variational Schr\"odinger and a rigorous Faddeev approach. It is argued that hybrid $Q\ensuremath{-}Q$ interactions with a sizable one-gluon-exchange component encounter difficulties in describing baryon spectra due to the specific contributions from one-gluon and meson exchanges together. In contrast, a chiral constituent quark model with a $Q\ensuremath{-}Q$ interaction relying solely on Goldstone-boson exchange is capable of providing a unified description not only of the $N$ and $\ensuremath{\Delta}$ spectra but also of all strange baryons in good agreement with phenomenology.