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Showing papers on "Meson published in 1994"



Journal ArticleDOI
TL;DR: The nuclear dependence of the diffractive cross sections provides important tests of color transparency as well as constraints on the shadowing of the gluon structure functions and the longitudinal structure functions of nuclei.
Abstract: We demonstrate that the distinctive features of the forward differential cross section of diffractive leptoproduction of a vector meson can be legitimately calculated in perturbative QCD in terms of the light-cone [ital q[bar q]] wave function of the vector meson and the gluon distribution of the target. In particular, we calculate the [ital Q][sup 2] and nuclear dependence of the diffractive leptoproduction of vector mesons and estimate the cross section. The production of longitudinally polarized vector mesons by longitudinally polarized virtual photons is predicted to be the dominant component, yielding a cross section behaving as [ital Q][sup [minus]6]. The nuclear dependence of the diffractive cross sections, which follows from a factorization theorem in perturbative QCD, provides important tests of color transparency as well as constraints on the shadowing of the gluon structure functions and the longitudinal structure functions of nuclei.

377 citations


Journal ArticleDOI
Estia Eichten1, Chris Quigg1
TL;DR: The spectrum of mesons is calculated using knowledge of the interaction between heavy quarks derived from the study of [ital c[bar c]] and [ital b[bar b]] bound states] and the prospects for experimental observation are considered.
Abstract: Applying knowledge of the interaction between heavy quarks derived from the study of [ital c[bar c]] and [ital b[bar b]] bound states, we calculate the spectrum of [ital c[bar b]] mesons. We compute transition rates for the electromagnetic and hadronic cascades that lead from excited states to the [sup 1][ital S][sub 0] ground state, and briefly consider the prospects for experimental observation of the spectrum.

353 citations


Journal ArticleDOI
F. Abe1, M. G. Albrow1, S. R. Amendolia1, D. Amidei1  +394 moreInstitutions (1)
TL;DR: In this paper, a search for the top quark with the Collider Detector at Fermilab (CDF) in a sample of pp collisions at √s=1.8 TeV with an integrated luminosity of 19.3±0.7 pb−1 is summarized.
Abstract: A search[1] for the top quark with the Collider Detector at Fermilab (CDF) in a sample of pp collisions at √s=1.8 TeV with an integrated luminosity of 19.3±0.7 pb−1 is summarized. We find 12 events consistent with either two W bosons, or a W boson and at least one b jet. The probability that the measured yield is consistent with the background is 0.26%. Though the statistics are too limited to establish firmly the existence of the top quark, a natural interpretation of the excess is that it is due to tt production. Under this assumption, constrained fits to individual events yield a top quark mass of 174±10+13−12 GeV/c2. The tt production cross section is measured to be 13.9+6.1−4.8 pb. Some implications of the measured value of the top mass are discussed.

276 citations


Journal ArticleDOI
TL;DR: The decays of resonances which have already been seen in the partial-wave analyses are examined, along with those of states which are predicted by the quark model but which remain undiscovered.
Abstract: We examine the decays of nonstrange baryons to the final states Delta Pi, NRho, NEta, NEta', Nw, N.5 (1440)Pi, and Delta 3/2+(1600)Pi, in a relativized pair-creation (^3Po) model which has been developed in a previous study of the NPi decays of the same baryon states.As it is our goal to provide a guide for the possible discovery of new baryon states at CEBAF and elsewhere, we examine the decays of resonances which have already been seen in the partial-wave analyses, along with those of states which are predicted by the quark model but which remain undiscovered.The level of agreement between our calculation and the available widths from the partial-wave analyses in encouraging.

268 citations


Journal ArticleDOI
TL;DR: An explicit quark model, based on a mean field description of nonoverlapping nucleon bags bound by the self-consistent exchange of σ, ω and ϱ mesons, is used to investigate the properties of both nuclear and neutron matter.

192 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present path-integral attempts to derive effective meson-baryon Lagrangians out of QCD or QCD-motivated quark models.

185 citations


Journal ArticleDOI
TL;DR: In this article, the decays of the [ital B][sub [ital c] meson are calculated systematically by introducing a suitable approach, and the obtained results are discussed and compared with those obtained by other approaches.
Abstract: The decays of the [ital B][sub [ital c]] meson are calculated systematically by introducing a suitable approach. The obtained results are discussed and compared with those obtained by other approaches.

181 citations


Journal ArticleDOI
TL;DR: In this paper, the authors employ an operator product expansion and the heavy quark effective theory to compute the leading corrections to the decay rate found in the free quark decay model, which is exact in the limit mb → ∞.
Abstract: We discuss nonperturbative contributions to the inclusive rare B decays B → Xsγ and B → Xsl + l − . We employ an operator product expansion and the heavy quark effective theory to compute the leading corrections to the decay rate found in the free quark decay model, which is exact in the limit mb → ∞. These corrections are of relative order 1/m 2 , and may be parameterised in terms of two low-energy parameters. We also discuss the corrections to other observables, such as the average photon energy in B → Xsγ and the lepton invariant mass spectrum in B → Xsl + l − .

169 citations


Journal ArticleDOI
TL;DR: In this paper, hyperon-nucleon interaction models A and B are presented, in which the explicit energy-dependence of the original models A, B of the Julich group is removed in order to simplify the application in nuclear structure calculations.

158 citations


Journal ArticleDOI
TL;DR: An explicit quark model, based on a mean field description of nonoverlapping nucleon bags bound by the self-consistent exchange of $\sigma$, $\omega$ and $\rho$ mesons, is used to investigate the properties of both nuclear and neutron matter as discussed by the authors.
Abstract: An explicit quark model, based on a mean field description of non-overlapping nucleon bags bound by the self-consistent exchange of $\sigma$, $\omega$ and $\rho$ mesons, is used to investigate the properties of both nuclear and neutron matter. We establish a clear understanding of the relationship between this model, which incorporates the internal structure of the nucleon, and QHD. Finally, we use the model to study the density dependence of the quark condensate in-medium.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the thermodynamics of a quark-meson plasma in the two-flavour Nambu-Jona-Lasinio (NJL) model.

Journal ArticleDOI
T. Ahmed1, S. Aid2, Vladimir Andreev, B. Andrieu3  +391 moreInstitutions (27)
TL;DR: In this paper, the H1 detector at HERA was used for a class of deep inelastic electron-proton scattering (DIS) events (5 < Q2 < 120 GeV2) at low Bjorken-x (10−4 < x < 10−2) which have almost no hadronic energy flow in a large interval of pseudo-rapidity around the proton remnant direction and which cannot be attributed to our present understanding of DIS and fluctuations in final state hadronic fragmentation.

Journal ArticleDOI
TL;DR: In this article, the authors discuss how the energy and Q2 dependence of elastic production of vector mesons at HERA will allow scanning the dipole cross-section as a function of dipole size r. They also present predictions for the effective intercept in the kinematic range of the forthcoming HERA experiments, which can shed much light on the nonperturbative component of the pomeron.

Journal ArticleDOI
TL;DR: In this article, four new quark-quark potentials were developed in the framework of the nonrelativistic quark model (NRQM), which can reproduce quite well the spectra of mesons and baryons.
Abstract: We present four new quark-quark potentials, developed in the framework of the nonrelativistic quark model (NRQM), which can reproduce quite well the spectra of mesons and baryons. They contain a central part which is of type “Coulomb+linear” or “Coulomb +2/3-power”, and a strong but smooth hyperfine term. With these four potentials and the one proposed by Bhaduri et al., we have calculated masses and decay properties of some interesting diquonia (q2q−2 mesons). We have not found appreciable difference between the results of the five potentials considered, indicating that the properties of diquonia are, to a large extent, potential-independent in the NRQM.

Journal ArticleDOI
TL;DR: In this paper, a detailed study of exclusive radiative rareB-decays in the framework of the QCD sum rules on the light cone was carried out, which combines the traditional QCDsum rule technique with the description of final state vector mesons in terms of the light-cone wave functions of increasing twist.
Abstract: We carry out a detailed study of exclusive radiative rareB-decays in the framework of the QCD sum rules on the light cone, which combines the traditional QCD sum rule technique with the description of final state vector mesons in terms of the light-cone wave functions of increasing twist. Our calculation is restricted to the leading twist-two operators. The decays considered are:Bu,d→K* +γ,Bu,d→p+γ,Bd→ω+γ and the corresponding decays of theBs mesons,Bs→ϕ+γ andBs→K*+γ. Based on our estimate of the transition form factorF1B→K* (0)=0.32±0.05, we find for the branching ratio BR(B→K*+γ)=(4.8±1.5)×10−5, which is in agreement with the observed value of (4.5±1.5±0.9)×10−5 measured by the CLEO collaboration. We present detailed estimates for the ratios of the radiative decay form factors, which are then used to predict the rates for the exclusive radiativeB-decays listed above. This in principle allows the extraction of the CKM matrix element |Vtd| from the penguin-dominated CKM-suppressed radiative decays when they are measured. We give a detailed discussion of the dependence of the radiative transition form factors on theb-quark mass and on the momentum transfer, as well as their interrelation with the CKM-suppressed semileptonic decay form factors in B→ρ+l+vl, which we also calculate in our approach.

Journal ArticleDOI
TL;DR: This work uses the QCD sum rule approach to calculate the splitting between vector and pseudoscalar mesons containing one light and one heavy quarks and the kinetic energy of the heavy quark.
Abstract: We use the QCD sum rule approach to calculate the splitting between vector and pseudoscalar mesons containing one light and one heavy quark and the kinetic energy of the heavy quark. Our result for the splitting induced by the chromomagnetic interaction agrees with the experimental data on charm and b-flavored mesons. For the matrix element of the kinetic energy operator, we obtain the value K=-(0.60±0.10) GeV2.

Journal ArticleDOI
TL;DR: This work studies meson decays mediated by the heavy gauge bosons of the Pati-Salam model of quark-lepton unification and considers the scenarios in which the [tau] lepton is associated with the third, second, and first generation of quarks.
Abstract: We study meson decays mediated by the heavy gauge bosons of the Pati-Salam model of quark-lepton unification. We consider the scenarios in which the \ensuremath{\tau} lepton is associated with the third, second, and first generation of quarks. The most sensitive probes, depending on the scenario, are rare K, \ensuremath{\pi}, and B decays.

Journal ArticleDOI
TL;DR: A nonperturbative parameter which measures the net transverse alignment of the light degrees of freedom in the fragmentation process is used to estimate the polarization retention of charm and bottom baryons.
Abstract: We discuss the production via fragmentation of excited heavy mesons and baryons, and their subsequent decay. In particular, we consider the question of whether a net polarization of the initial heavy quark may be detected, either in a polarization of the final ground state or in anisotropies in the decay products of the excited hadron. The result hinges in part on a nonperturbative parameter which measures the net transverse alignment of the light degrees of freedom in the fragmentation process. We use existing data on charmed mesons to extract this quantity for certain excited mesons. Using this result we estimate the polarization retention of charm and bottom baryons.

Journal ArticleDOI
Thomas Mannel1
TL;DR: In this article, the first nonvanishing corrections to the parton model result are given and the lepton energy spectrum of inclusive semileptonic decays of heavy mesons is calculated.

Journal ArticleDOI
TL;DR: This work calculates the effective mass of the [omega] meson in nuclear matter in a relativistic random-phase approximation to the Walecka model and reports a reduction in the meson mass of about 170 MeV at nuclear-matter saturation density.
Abstract: We calculate the effective mass of the [omega] meson in nuclear matter in a relativistic random-phase approximation to the Walecka model. The dressing of the meson propagator is driven by its coupling to particle-hole pairs and nucleon-antinucleon ([ital N[bar N]]) excitations. We report a reduction in the [omega]-meson mass of about 170 MeV at nuclear-matter saturation density. This reduction arises from a competition between the density-dependent (particle-hole) dressing of the propagator and vacuum polarization ([ital N[bar N]] pairs). While density-dependent effects lead to an increase in the mass proportional to the classical plasma frequency, vacuum polarization leads to an even larger reduction caused by the reduced effective nucleon mass in the medium.

Journal ArticleDOI
TL;DR: In this article, the mass of the ω-meson decreases in nuclear medium using the Walecka model and the physical origin of the decrease is a reduction of the wave function renormalization constant induced by the ϱNN tensor coupling.

Journal ArticleDOI
TL;DR: In this paper, a scaling relation between the ϱ 0 and the J / Ψ production was proposed to test the mechanism of colour transparency in exclusive (virtual) photoproduction.

Journal ArticleDOI
TL;DR: In this article, the baryon resonances up to 2 GeV were taken into account coherently in the calculations of the πN→∑K process and the shape of the total cross sections for different isospin projections were analyzed.

Journal ArticleDOI
R.J. Akers1, Gideon Alexander2, John Allison1, K. J. Anderson3  +321 moreInstitutions (31)
TL;DR: In this article, the authors compared the JETSET and HERWIG Monte Carlo models with the OPAL detector at LEP and found that both models agree with the observed data.
Abstract: The inclusive production rates of π±,K± andp\(\bar p\) inZ0 decays have been measured with the OPAL detector at LEP. Using the energy loss measurement in the jet chamber, the momentum range up to the beam energy (45.6 GeV/c) has been covered. Differential cross sections and total particle yields are given. Comparisons of the inclusive momentum spectra and the total rates with predictions of the JETSET and the HERWIG Monte Carlo model are presented. The total single rates are found to be 17.05±0.43 π±, 2.42±0.13K± and 0.92±0.11p\(\bar p\) per hadronic event. Predictions of JETSET for cross sections and total rates agree very well for π±; however, for momenta greater than 4 GeV/c,K± rates are underestimated and\(\bar p\) rates are overestimated. Combined with data of other particle species there is evidence that the peak positions in the ξ=ln(1/x p ) distributions show a different mass dependence for mesons and baryons. However, both JETSET and HERWIG Monte Carlo predictions agree with the observed data.

Journal ArticleDOI
TL;DR: In this paper, a study of finite a and volume effects of heavy pseudoscalar mesons in the static approximation was performed on a number of lattices at β = 5.74, 6.0 and 6.26 covering sizes from about 0.7 fm to 2 fm.

Journal ArticleDOI
TL;DR: In this article, the authors studied the thermodynamics of a quark plasma in the two-flavour Nambu-Jona-Lasinio model and derived the second virial coefficient for a gas of non-relativistic particles.

Journal ArticleDOI
TL;DR: In this article, a formalism for the introduction of collective degrees of freedom at some intermediate scale and derive the corresponding evolution equations is developed, which allows the appearance of bound states at some characteristic length scale as, for example, the mesons in QCD.

Journal ArticleDOI
TL;DR: If the standard model explanation of $CP$ violation is correct, then measurements of $\mathrm{CP}$-violating asymmetries in $B$ meson decays can in principle determine the entire quark mixing matrix.
Abstract: If the standard model explanation of $\mathrm{CP}$ violation is correct, then measurements of $\mathrm{CP}$-violating asymmetries in $B$ meson decays can in principle determine the entire quark mixing matrix.

Journal ArticleDOI
TL;DR: In this article, a general relationship is formulated between the contributions of weak annihilation to the semileptonic decays of heavy flavour hadrons and the matrix elements of four-fermion operators.