Showing papers on "Meson published in 1993"
TL;DR: The lepton spectrum in semileptonic [ital b] decays is derived from a nonperturbative treatment of QCD; it is based on an expansion in 1/[ital m][sub [ital Q]][sup 2] terms with [ital m] being the heavy flavor quark mass.
Abstract: We derive the lepton spectrum in semileptonic [ital b] decays from a nonperturbative treatment of QCD; it is based on an expansion in 1/[ital m][sub [ital Q]] with [ital m][sub [ital Q]] being the heavy flavor quark mass. The leading corrections arising on the 1/[ital m][sub [ital Q]] level are completely expressed in terms of the difference in the mass of the heavy hadron and the quark. Nontrivial effects appear in 1/[ital m][sub [ital Q]][sup 2] terms affecting mainly the end-point region; they are different for meson and baryon decays as well as for bottom and charm decays.
350 citations
TL;DR: In this paper, the long-range binding potential is computed using one-pion exchange between ground state Q q mesons and computed using chiral perturbation theory, which may be sufficiently attractive to produce a weakly bound two-meson state.
190 citations
TL;DR: The fragmentation functions describing the splitting of charm quarks into S-wave charmonium states to leading order in the QCD coupling constant are calculated and agree with the complete leading order calculation of the rate for Z 0 → ψcc.
Abstract: In decays of the [ital Z][sup 0], the dominant mechanism for the direct production of charmonium states is the decay of the [ital Z][sup 0] into a charm quark or antiquark followed by its fragmentation into the charmonium state. We calculate the fragmentation functions describing the splitting of charm quarks into [ital S]-wave charmonium states to leading order in the QCD coupling constant. Leading logarithms of [ital M][sub [ital Z]]/[ital m][sub [ital c]] are summed up using Altarelli-Parisi evolution equations. Our analytic result agrees with the complete leading order calculation of the rate for [ital Z][sup 0][r arrow][psi][ital c[bar c]]. We also use our fragmentation functions to calculate the production rate of heavy quarkonium states in [ital W][sup [plus minus]], top quark, and Higgs boson decays.
178 citations
TL;DR: In this article, the properties of ϱ-mesons in vacuum and nuclear matter were studied in a hadronic model which satisfies unitarity and current conservation, including the coupling of the ϱmeson to two pions which, in matter, are strongly mixed with delta-particle-nucleon-hole states.
178 citations
TL;DR: In this article, the authors reexamine the question of isospin analysis applied to the [rho][pi] decay modes of the [ital B] as a tool to extract the CKM angle between [ital V][sub [ital u][ital b]][sup *][ital V] and [ital U][ital d] without ambiguities or uncertainties due to penguin amplitude contributions, and find that a maximum-likelihood fit of the parameters to the full Dalitz plot distribution can successfully extract the parameters.
Abstract: We reexamine the question of isospin analysis applied to the [rho][pi] decay modes of the [ital B] as a tool to extract the CKM angle between [ital V][sub [ital u][ital b]][sup *][ital V][sub [ital u][ital d]] and [ital V][sub [ital t][ital b]][sup *][ital V][sub [ital t][ital d]], without ambiguities or uncertainties due to penguin amplitude contributions. We find that a maximum-likelihood fit of the parameters to the full Dalitz plot distribution can successfully extract the parameters---perhaps with as few as 1000 events. This result is from a study of Monte Carlo--generated events without inclusion of detector efficiency or background effects. The interference between channels is a large effect and provides additional constraints on the parameters compared to channel-by-channel studies. These can usually lift the degeneracy between the multiple solutions that plague such studies. The inclusion of charged [ital B] decays in the analysis would provide a direct check of the standard model prediction that the penguin amplitude weak phase for this channel is canceled by the weak mixing phase.
176 citations
TL;DR: In this article, a new formulation of QCD sum rules at finite temperature (T) is developed, where all the soft dynamics including the effect of finite T in the hadronic phase is taken into account in the thermal average of local operators.
150 citations
TL;DR: In this article, the branching ratio for φ → KKγ via φ→ Sγ (where S denotes one of the scalar mesons f0(975) and a0(980) vary by several orders of magnitude.
146 citations
TL;DR: A new precision measurement of the branching ratio of the rare pion decay into a positron and a neutrino ([pi][r arrow][ital e][nu]) has been completed.
Abstract: A new precision measurement of the branching ratio of the rare pion decay into a positron and a neutrino ([pi][r arrow][ital e][nu]) has been completed. A beam of positive pions was stopped in an active target of plastic scintillator surrounded by a 4[pi] BGO calorimeter. 3[times]10[sup 5] rare decays and 1.2[times]10[sup 6] normal pion decays ([pi][r arrow][mu][nu]) were recorded. The branching ratio was finally calculated from 1.2[times]10[sup 5] rare decays after various cuts in the time window from 7.5 to 200 ns after pion stop. The errors of the result (1.235[plus minus]0.005)[times]10[sup [minus]4] are 0.28% statistical and 0.29% systematical.
143 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, an effective lagrangian including negative and positive parity heavy mesons containing a heavy quark, light pseudoscalars, and light vector resonances, with their allowed interactions, was introduced.
115 citations
TL;DR: In this paper, the cross section for coherent nuclear processes in which an incident meson or photon dissociates diffractively into two jets of high relative transverse momentum (between about 1 and 3 GeV/c) is found to be proportional in QCD to A2 in a wide kinematical region.
TL;DR: Relativistic mean field theory in the rotating frame is used to describe superdeformed nuclei and identical bands in neighboring rare earth nuclei are investigated, with excellent agreement with recent experimental data.
Abstract: Relativistic mean field theory in the rotating frame is used to describe superdeformed nuclei. Nuclear currents and the resulting spatial components of the vector meson fields are fully taken into account. Identical bands in neighboring rare earth nuclei are investigated and excellent agreement with recent experimental data is observed.
TL;DR: An effective action combining chiral and heavy-quark symmetry is derived, using approximate bosonization techniques to QCD-inspired models of spontaneous symmetry breaking, and the relevance of this effective action to solitons with heavy quarks is briefly discussed.
Abstract: We derive an effective action combining chiral and heavy-quark symmetry, using approximate bosonization techniques to QCD-inspired models of spontaneous symmetry breaking. We explicitly show that the heavy-quark limit is compatible with the large [ital N][sub [ital c]] (number of color) limit in the meson sector, and estimate the couplings between the light and heavy mesons ([ital D],[ital D][sup *], . . .) and their chiral partners to order one in the heavy-quark mass. The relevance of this effective action to solitons with heavy quarks is briefly discussed.
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.
TL;DR: In this paper, the authors show that CP violating asymmetries in neutral B mesons decays is more general, resulting from a much wider class of models for quark masses.
TL;DR: In this paper, the measurement of the τ from the energy distributions of its decay products is studied for the various decay channels: τ → πν, ϱν, a1ν, lνν, and in particular the model dependence of the description of τ → (3π)ν decay is examined.
TL;DR: Semileptonic decay of the Bc meson in the heavy quark limit was studied in this article, where six possible form factors for B c → B s (B 0 ), B s ∗ (B ∗0 ) semileptic decay are determined by two invariant functions.
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TL;DR: In this article, the authors review the current status of heavy quark symmetry and its applications to weak decays of hadrons containing a single quark, including a comprehensive treatment of symmetry breaking corrections.
Abstract: We review the current status of heavy quark symmetry and its applications to weak decays of hadrons containing a single heavy quark. After an introduction to the underlying physical ideas, we discuss in detail the formalism of the heavy quark effective theory, including a comprehensive treatment of symmetry breaking corrections. We then illustrate some nonperturbative approaches, which aim at a dynamical, QCD-based calculation of the universal form factors of the effective theory. The main focus is on results obtained using QCD sum rules. Finally, we perform an essentially model-independent analysis of semileptonic $B$ meson decays in the context of the heavy quark effective theory.
TL;DR: Using a cross-section distribution for pionic projectiles on nucleons consistent with the data on the moments of the distribution, the probability for a pion to be in a pointlike configuration is calculated and predictions based on a combination of perturbative QCD and QCD sum rules are compared.
Abstract: The scattering of hadrons at high energies can be described by a distribution function of cross sections, which incorporates the phenomena of color transparency and color opacity. We infer here a cross-section distribution for pionic projectiles on nucleons consistent with the data on the moments of the distribution. Using this distribution we calculate the probability for a pion to be in a pointlike configuration and compare with predictions based on a combination of perturbative QCD and QCD sum rules. Comparison with the corresponding distribution for nucleon-nucleon scattering shows that color transparency effects should be more pronounced for a meson beam.
TL;DR: In this article, the wave function of vector mesons on nuclei is computed based on color transparency and QCD predicted spatial wave functions of quark-antiquark fluctuations of virtual photons.
TL;DR: In this article, the decay widths of the B c meson were evaluated by QCD sum rules and the possibility of discovering this meson at present and future high energy machines was discussed.
Abstract: Leptonic and semileptonic decay widths of theB c meson, as well as its mass, are evaluated by QCD sum rules. The possibility of discovering this meson at present and future high energy machines is also discussed.
TL;DR: In this paper, an analysis of two-body non-leptonic decays of B and Bs mesons in the factorization approximation was performed, using the semileptonic decay amplitudes calculated on the basis of an effective lagrangian satisfying chiral and heavy quark symmetries.
TL;DR: Using this formalism, it is shown how the nucleon’s transversity distribution can be measured in single pion inclusive electroproduction.
Abstract: We define twist-two and twist-three quark fragmentation functions in quantum chromodynamics and study their physical implications. Using this formalism we show how the nucleon's transversity distribution can be measured in single pion inclusive electroproduction.
TL;DR: In this paper, a model for electro-and photo-pion production is presented which is applicable at threshold and through the first and second resonance regions, and a detailed comparison with experiment is found with data on the proton target than with the neutron target.
TL;DR: In this paper, the Isgur-Wise function for Λ b → Λ c e − ν e decay is computed in the large-Nc limit, where the soliton and heavy meson are bound in an attractive harmonic oscillator potential.
TL;DR: In this article, the rare decay b → sγ is discussed in supersymmetric standard models based on grand unification and N = 1 supergravity and the interaction lagrangians which induce the generation changings for the quarks are given in explicit forms.
TL;DR: It is demonstrated that pionic double charge exchange reaction features find their natural explanation by a narrow resonance in the [pi][ital NN] subsystem with [ital J][sup [ital P]]=0[sup [minus]] and a mass of 2.065 GeV.
Abstract: All currently available data on the pionic double charge exchange reaction ([pi][sup +],[pi][sup [minus]]) on nuclei exhibit a very peculiar energy dependence near [ital T][sub [pi]]=50 MeV, while the angular distributions behave quite regularly. We demonstrate that these features find their natural explanation by a narrow resonance in the [pi][ital NN] subsystem with [ital J][sup [ital P]]=0[sup [minus]] and a mass of 2.065 GeV.
TL;DR: In this article, the cross sections of the [ital B][sub [ital c] meson at the energies reached at the Tevatron, LHC, and SSC or higher were calculated.
Abstract: Based on a reliable mechanism, the cross sections of the [ital B][sub [ital c]] hadronic production at the TeV energies of the CERN S[ital p[bar p]]S, Fermilab Tevatron, CERN LHC, and SSC, as well as their possible fixed target experiments, are calculated. The results are presented numerically and indicate that the cross sections at the energies reached at the Tevatron, LHC, and SSC or higher are sufficiently large for further considering experimental studies of the [ital B][sub [ital c]] meson at these colliders.
TL;DR: In this paper, the authors demonstrate how the color transparency effect leads to a belated onset of color transparency effects as a function of the size of quark configurations in the exclusive production of vector mesons on nuclei.
Abstract: The exclusive production of vector mesons in deep inelastic scattering is a hard scattering process with the well controlled size of quark configurations which dominate the production amplitude. This allows an unambiguous prediction of color transparency effects in the coherent and incoherent production of vector mesons on nuclei. We demonstrate how the very mechanism of color transparency leads to a belated onset of color transparency effects as a function of $Q^{2}$. We conclude that the $Q^{2}$ dependence of the exclusive $\rho^{0}$-meson production on nuclei and nucleons observed in the Fermilab E665 experiment gives a solid evidence for the onset of color transparency. We propose the scaling relation between the $\rho^{0}$ and the $J/\Psi$ production, which further tests the mechanism of color transparency in exclusive (virtual) photoproduction.
TL;DR: In this article, the wave function of vector mesons on nuclei is computed using color transparency and QCD predicted spatial wave functions of quark-antiquark fluctuations of virtual photons, and a rich, energy and $Q^{2}$-dependent, pattern of nuclear shadowing and antishadowing is predicted.
Abstract: We demonstrate how the virtual photoproduction of vector mesons on nuclei scans the wave function of vector mesons from the large non-perturbative transverse size $\rho \sim R_{V}$ down to the small perturbative size $\rho \sim 1/\sqrt{Q^{2}}$. Thee mechanism of scanning is based on color transparency and QCD predicted spatial wave function of quark-antiquark fluctuations of virtual photons. A rich, energy- and $Q^{2}$-dependent, pattern of the nuclear shadowing and antishadowing is predicted, which can be tested at the European Electron Facility and SLAC.