Showing papers on "Meson published in 2002"
TL;DR: In this article, it was shown that two nonets and a glueball provided a consistent description of data on scalar mesons below 1.7 GeV, and a simple effective chiral model for such a system with two scalar nonets can be made involving two coupled linear sigma models.
Abstract: We show that two nonets and a glueball provide a consistent description of data on scalar mesons below 1.7 GeV. Above 1 GeV the states form a conventional q nonet mixed with the glueball of lattice QCD. Below 1 GeV the states also form a nonet, as implied by the attractive forces of QCD, but of a more complicated nature. Near the centre they are (qq)()3 in S-wave, with some q in P-wave, but further out they rearrange as (q)1(q)1 and finally as meson–meson states. A simple effective chiral model for such a system with two scalar nonets can be made involving two coupled linear sigma models. One of these could be looked upon as the Higgs sector of nonpertubative QCD.
292 citations
TL;DR: In this article, the relativistic Hartree-Bogoliubov (RHB) model is extended to include density-dependent meson-nucleon couplings, and the new densitydependent effective interaction DD-ME1 is tested in the analysis of the equations of state for symmetric and asymmetric nuclear matter, and of groundstate properties of the Sn and Pb isotopic chains.
Abstract: The relativistic Hartree-Bogoliubov (RHB) model is extended to include density-dependent meson-nucleon couplings. The effective Lagrangian is characterized by a phenomenological density dependence of the $\ensuremath{\sigma},$ $\ensuremath{\omega},$ and $\ensuremath{\rho}$ meson-nucleon vertex functions, adjusted to properties of nuclear matter and finite nuclei. Pairing correlations are described by the pairing part of the finite range Gogny interaction. The new density-dependent effective interaction DD-ME1 is tested in the analysis of the equations of state for symmetric and asymmetric nuclear matter, and of ground-state properties of the Sn and Pb isotopic chains. Results of self-consistent RHB calculations are compared with experimental data, and with results previously obtained in the RHB model with nonlinear self-interactions, as well as in the density-dependent relativistic hadron field (DDRH) model. Parity-violating elastic electron scattering on Pb and Sn nuclei is calculated using a relativistic optical model with inclusion of Coulomb distortion effects, and the resulting asymmetry parameters are related to the neutron ground-state density distributions.
242 citations
TL;DR: In this article, the effects of coupling to an isovector-scalar meson in a phenomenological hadronic field theory have been investigated for the equation of state and the phase diagram of asymmetric nuclear matter.
Abstract: We try to single out some qualitative effects of coupling to a \ensuremath{\delta}-isovector-scalar meson, introduced in a minimal way in a phenomenological hadronic field theory. Results for the equation of state (EOS) and the phase diagram of asymmetric nuclear matter (ANM) are discussed. We stress the consistency of the \ensuremath{\delta}-coupling introduction in a relativistic approach. Contributions to the slope and curvature of the symmetry energy and to the neutron-proton effective mass splitting appear particularly interesting. A more repulsive EOS for neutron matter at high baryon densities is expected. Effects on the critical properties of warm ANM, mixing mechanical and chemical instabilities and isospin distillation, are also presented. The \ensuremath{\delta} influence is mostly on the isovectorlike collective response. The results are largely analytical, and this makes the physical meaning quite transparent. Implications for nuclear structure properties of drip-line nuclei and for reaction dynamics with radioactive beams are finally pointed out.
207 citations
TL;DR: In this article, the S-wave interaction of mesons with baryons in the strangeness S = 0 sector in a coupled channel unitary approach is studied and the basic dynamics are drawn from the lowest order meson baryon chiral Lagrangians.
Abstract: We study the S-wave interaction of mesons with baryons in the strangeness S=0 sector in a coupled channel unitary approach. The basic dynamics is drawn from the lowest order meson baryon chiral Lagrangians. Small modifications inspired by models with explicit vector meson exchange in the t-channel are also considered. In addition the pi pi N channel is included and shown to have an important repercussion in the results, particularly in the isospin 3/2 sector.
203 citations
TL;DR: In this article, a complete one-loop calculation of all the two-meson scattering amplitudes within the framework of SU(3) chiral perturbation theory was presented, including pions, kaons, and the eta.
Abstract: We present a complete one-loop calculation of all the two-meson scattering amplitudes within the framework of SU(3) chiral perturbation theory, which includes pions, kaons, and the eta. In addition, we have unitarized these amplitudes with the coupled channel inverse amplitude method, which simultaneously ensures the good low energy properties of chiral perturbation theory and unitarity. We show how this method provides a remarkable description of meson-meson scattering data up to 1.2 GeV including the scattering lengths and the generation of seven light resonances, which is consistent with previous determinations of the chiral parameters. Particular attention is paid to discussing the differences and similarities of this work with previous analyses in the literature.
194 citations
TL;DR: In this article, the cross-section of the process e+e−→π+π− has been measured using about 11,4000 events collected by the CMD-2 detector at the VEPP-2M e−e− collider in the center-of-mass energy range from 0.61 to 0.96 GeV.
185 citations
TL;DR: In this article, the nucleon-antinucleon scattering experiments performed at the Low Energy Antiproton Ring (LEAR) of CERN are reviewed and the underlying physics is discussed, in particular by comparison with the predictions of current models based on meson exchange and shortrange absorption.
185 citations
TL;DR: In this article, the strangeness-changing scalar form factors are derived, which incorporate known theoretical constraints both at low and high energies, and a set of short-distance constraints on the scalar resonance couplings is obtained, imposing the form factors to vanish at infinite momentum transfer.
170 citations
TL;DR: In this article, the effect of SU(3)-flavor breaking on high-density quark matter was studied, in particular a nonzero electron chemical potential and a finite strange-quark mass.
169 citations
TL;DR: In this paper, the amplitude of the CP asymmetry is derived from the decay-time distributions in such events, which is consistent with the standard model expectation of no direct CP violation in these modes.
Abstract: We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 88 x 10(6) Upsilon(4S)-->B(-)B decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We study events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B(0) or B(-0) from its decay products. The amplitude of the CP asymmetry, which in the standard model is proportional to sin2beta, is derived from the decay-time distributions in such events. We measure sin2beta=0.741+/-0.067(stat)+/-0.034(syst) and |lambda|=0.948+/-0.051(stat)+/-0.030(syst). The magnitude of lambda is consistent with unity, in agreement with the standard model expectation of no direct CP violation in these modes.
157 citations
TL;DR: In this paper, a relativistic and unitary approach to high energy pion-and photon-nucleon reactions is presented, taking the πN, πΔ, ρN, ωN, ηN, KΛ, KΣ final states into account.
TL;DR: In this article, the mass spectrum of charmed and bottom baryons is computed on anisotropic lattices using quenched lattice nonrelativistic QCD.
Abstract: The mass spectrum of charmed and bottom baryons is computed on anisotropic lattices using quenched lattice nonrelativistic QCD. The masses are extracted by using mass splittings which are more accurate than masses obtained directly by using the nonrelativistic mass-energy relation. Of particular interest are the mass splittings between spin-1/2 and spin-3/2 heavy baryons, and we find that these color hyperfine effects are not suppressed in the baryon sector although they are known to be suppressed in the meson sector. The results are compared with those obtained in a previous nonrelativistic QCD calculation and with those obtained from a Dirac-Wilson action of the D234 type.
TL;DR: In this article, a covariant approach was developed to describe low-lying scalar, pseudoscalar, vector, and axial-vector mesons as quark-antiquark bound states.
Abstract: We develop a covariant approach to describe the low-lying scalar, pseudoscalar, vector, and axial-vector mesons as quark-antiquark bound states. This approach is based on an effective interaction modeling the nonperturbative structure of the gluon propagator that enters the quark Schwinger-Dyson and meson Bethe-Salpeter equations. We consistently treat these integral equations by precisely implementing the quark propagator functions that solve the Schwinger-Dyson equations into the Bethe-Salpeter equations in the relevant kinematical region. We extract the meson masses and compute the pion and kaon decay constants. We obtain a quantitatively correct description for pions, kaons, and vector mesons while the calculated spectra of scalar and axial-vector mesons suggest that their structure is more complex than being quark-antiquark bound states.
TL;DR: The authors measured the branching ratio of φ mesons with the KLOE detector using a sample of ∼5×10 7 φ decays and fit the two-pion mass spectrum to models to disentangle contributions from various sources.
TL;DR: In this paper, the branching ratio of the Frascati φ -factory was measured with the KLOE detector using a sample of ∼5×10 7 φ mesons.
TL;DR: In this paper, the meson and diquark bound states using the rainbow-ladder truncation of QCD's Dyson-Schwinger equations were studied using two parameters.
Abstract: We study meson and diquark bound states using the rainbow-ladder truncation of QCD’s Dyson-Schwinger equations. The infrared strength of the rainbow-ladder kernel is described by two parameters. The ultraviolet behavior is fixed by the one-loop renormalization group behavior of QCD, which ensures the correct asymptotic behavior of the Bethe-Salpeter amplitudes and brings important qualitative benefits. The diquark with the lowest mass is the scalar, followed by the axialvector and pseudoscalar diquark. This ordering can be anticipated from the meson sector.
TL;DR: In this paper, the angular distribution of gammap-etap has been measured with tagged real photons for incident photon energies from 0.75 to 1.95 GeV using kinematical information for protons scattered in the production process.
Abstract: Differential cross sections for gammap-->etap have been measured with tagged real photons for incident photon energies from 0.75 to 1.95 GeV. Mesons were identified by missing mass reconstruction using kinematical information for protons scattered in the production process. The data provide the first extensive angular distribution measurements for the process above W=1.75 GeV. Comparison with preliminary results from a constituent quark model support the suggestion that a third S11 resonance with mass approximately 1.8 GeV couples to the etaN channel.
TL;DR: In this paper, the branching ratios for these decays were evaluated in the framework of minimal gravity-, gauge-and anomaly-mediated SUSY breaking models, and also in SU(5) supergravity models with nonuniversal gaugino mass parameters at the GUT scale.
Abstract: If tan(beta) is large, down-type quark mass matrices and Yukawa couplings cannot be simultaneously diagonalized, and flavour violating couplings of the neutral Higgs bosons are induced at the 1-loop level. These couplings lead to Higgs-mediated contributions to the decays B_s -> mu+ mu- and B_d -> tau+ tau-, at a level that might be of interest for the current Tevatron run, or possibly, at B-factories. We evaluate the branching ratios for these decays within the framework of minimal gravity-, gauge- and anomaly-mediated SUSY breaking models, and also in SU(5) supergravity models with non-universal gaugino mass parameters at the GUT scale. We find that the contribution from gluino loops, which seems to have been left out in recent phenomenological analyses, is significant. We explore how the branching fraction varies in these models, emphasizing parameter regions consistent with other observations.
TL;DR: The field of meson production at threshold in the hadron-hadron interaction began in the fifties when sufficient energies of accelerated protons were available as discussed by the authors, and the field is entering a new domain of precision.
TL;DR: In this paper, it was shown that dynamical generation of physical states is a possible solution to the problem of accounting for more scalar mesons than can fit in a single nonet, as experiments clearly deliver.
Abstract: Starting with just one bare seed for each member of a scalar nonet, we investigate when it is possible to generate more than one hadronic state for each set of quantum numbers. In the framework of a simple model, we find that in the $I=1$ sector it is possible to generate two physical states with the right features to be identified with the ${a}_{0}(980)$ and the ${a}_{0}(1450).$ In the $I=1/2$ sector, we can generate a number of physical states with masses higher than 1 GeV, including one with the right features to be associated with the ${K}_{0}^{*}(1430).$ However, a light $\ensuremath{\kappa}$ scalar meson cannot be generated as a conventional resonance but only as a bound state. The $I=0$ sector is the most complicated and elusive: since all outcomes are very strongly model dependent, we cannot draw any robust conclusion. Nevertheless, we find that in that case too, depending on the coupling scheme adopted, the occurrence of numerous states can be achieved. This shows that dynamical generation of physical states is a possible solution to the problem of accounting for more scalar mesons than can fit in a single nonet, as experiments clearly deliver.
TL;DR: The first observation of rho(0) photoproduction, AuAu-->AuAurho( 0), and rho (0) production accompanied by mutual nuclear Coulomb excitation in ultraperipheral heavy-ion collisions was reported by the STAR Collaboration as mentioned in this paper.
Abstract: The STAR Collaboration reports the first observation of exclusive rho(0) photoproduction, AuAu-->AuAurho(0), and rho(0) production accompanied by mutual nuclear Coulomb excitation, AuAu-->Au*Au*rho(0), in ultraperipheral heavy-ion collisions. The rho(0) have low transverse momenta, consistent with coherent coupling to both nuclei. The cross sections at sqrt[s(NN)]=130 GeV agree with theoretical predictions treating rho(0) production and Coulomb excitation as independent processes.
TL;DR: In this paper, the decay constant of the pseudo-scalar heavy-light mesons in the heavy quark effective theory framework of QCD sum rules is derived from the non-relativistic sum rules for π π resonances in the next to next-to-leading approximation.
Abstract: In this paper we compute the decay constant of the pseudo-scalar heavy-light mesons in the heavy quark effective theory framework of QCD sum rules. In our analysis we include the recently evaluated three-loop result of order $\alpha_s^2$ for the heavy-light current correlator. The value of the bottom quark mass, which essentially limits the accuracy of the sum rules for $B$ meson, is extracted from the nonrelativistic sum rules for $\Upsilon$ resonances in the next-to-next-to-leading approximation. We find stability of our result with respect to all types of corrections and the specific form of the sum rule which reduces the uncertainty. Our results $f_B=206\pm 20$ MeV and $f_D=195\pm 20$ MeV for the $B$ and $D$ meson decay constants are in impressive agreement with recent lattice calculations.
TL;DR: The region of the S11(1535) resonance is fully covered in a photoproduction experiment and will allow a precise extraction of its parameters at the photon point as discussed by the authors.
TL;DR: In this paper, the authors study the process B−→K−χc0 considering intermediate charmed meson rescattering effects and find that rescattering effect is able to produce a large branching ratio consistent with measurements by Belle Collaboration.
TL;DR: In this article, the authors studied the contribution of D*+/-(2010) mesons in deep-inelastic scattering with the HI detector at HERA and determined the charm contribution to the proton structure, F-c(2)(x, Q(2)), by extrapolating the visible charm cross section to the full phase space.
TL;DR: In this paper, perturbative QCD corrections to the lifetime splitting between the charged and neutral B meson in the framework of the heavy quark expansion are computed, where the uncertainties associated with the choices of renormalization scale and scheme significantly reduced compared to the leading-order result.
TL;DR: In this article, the authors used the valon-recombination model to determine the x distributions of the data on inclusive cross sections, except for the normalizations since the data are at fixed p{T}.
Abstract: Inclusive distributions of soft production of mesons in hadronic collisions are calculated in the valon-recombination model. The new determination of the valon distributions from hard scattering data makes possible a tightly interrelated treatment of pion and kaon production in the fragmentation regions of proton, pion, and kaon. Only one free parameter is used in the determination of the valon distribution in the kaon. No other adjustable parameter is needed to fit the x distributions of the data on inclusive cross sections, except for the normalizations since the data are at fixed ${p}_{T}.$ The success of the model in reproducing seven inclusive distributions suggests that there are two important mechanisms at work in soft production. One is that the structure of the hadron that fragments is highly relevant. The other is that the produced particles are formed by the recombination of quarks and antiquarks. These two aspects about hadrons in soft processes can be well described in the framework of the valon-recombination model.
TL;DR: In this article, the CP-averaged branching ratios and CP-violating asymmetries of two-body charmless hadronic decays of B-s-->PP,PV with the QCD factorization approach were calculated.
Abstract: We calculate the CP-averaged branching ratios and CP-violating asymmetries of two-body charmless hadronic decays of B-s-->PP,PV with the QCD factorization approach (here P and V denote pseudoscalar and vector mesons, respectively), including contributions from the chirally enhanced power corrections and weak annihilations. Only several decay modes, such as B-s-->(KK)-K-(*), K((*)+/-)pi(-/+), K(+/-)rho(-/+), eta(('))eta((')), have large branching ratios, which may be observed in the near future. We also discuss B-s-->K+K-, K-0(K) over bar (0) decays which could overconstrain the penguin-to-tree ratio \P-pipi/T-pipi\ of B-->pi(+)pi(-) decays and give a bound on the Cabibbo-Kobayashi-Maskawa angle gamma.
TL;DR: In this article, the Borel sum rule for the three-point function of one pseudoscalar, one axial and one vector meson currents was evaluated for both off-shell and on-shell mesons.
Abstract: The $D^*D\pi$ form factor is evaluated in a QCD sum rule calculation for both $D$ and $\pi$ off-shell mesons. We study the Borel sum rule for the three-point function of one pseudoscalar, one axial and one vector meson currents. We find that the momentum dependence of the form factors is very different if the $D$ or the $\pi$ meson is off-shell, but they lead to the same coupling constant in the $D^*D\pi$ vertex.
TL;DR: In this paper, a set of finite energy sum rules (FESR) is used to determine the light quark mass of the first excited pseudoscalar mesons in the isovector vector channel.
Abstract: The flavor $\mathrm{ud}$ and $\mathrm{us}$ pseudoscalar correlators are investigated using families of finite energy sum rules (FESR's) known to be very accurately satisfied in the isovector vector channel. It is shown that the combination of constraints provided by the full set of these sum rules is sufficiently strong to allow determination of both the light quark mass combinations ${m}_{u}{+m}_{d},$ ${m}_{s}{+m}_{u}$ and the decay constants of the first excited pseudoscalar mesons in these channels. The resulting masses and decay constants are also shown to produce well-satisfied Borel transformed sum rules, thus providing nontrivial constraints on the treatment of direct instanton effects in the FESR analysis. The values of ${m}_{u}{+m}_{d}$ and ${m}_{s}{+m}_{u}$ obtained are in good agreement with the values implied by recent hadronic $\ensuremath{\tau}$ decay analyses and the ratios obtained from ChPT. New light quark mass bounds based on FESR's involving weight functions which strongly suppress spectral contributions from the excited resonance region are also presented.