879 research outputs found

    Leading/nonleading Charm Hadroproduction in the Quark-Gluon String Model

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    Leading charm production in reaction πNDX\pi^- N \rightarrow DX is discussed.Three experiments at Fermilab and CERN have measured a rather large enhancement in production rate of leading DD^--mesons over nonleading D+D^+.A good description of these results is obtained in Quark Gluon String Model (QGSM) if the idea of 'intrinsic charm' is involved. The weight of the ccˉc\bar{c} pairs in the quark sea of colliding hadrons is estimated from the experimental data. The comparison with other theoretical models is also carried out.Comment: 5 pages,LATEX, 3 figures are available from author (by FAX) upon reques

    Open charm and beauty production in hadron reactions

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    The production of charmed and beauty hadrons in proton-proton and proton-antiproton collisions at high energies is analyzed within the modified quark-gluon string model (QGSM) including the internal motion of quarks in colliding hadrons. It is shown that using both the QGSM and NLO QCD one can describe the experimental data rather successfully in a wide region of transverse momenta. We also present some predictions for the future experiments on the beauty baryon production in pppp collisions at LHC energies and on the charmed meson production in pˉp{\bar p}p reactions at GSI energies.Comment: 8 pages, 10 figures. Talk given at International Conference on Hadron Structure (HS 09), Tatranska Strba, Slovak Republic, August 29th-September 3rd, 200

    J/psi c\bar{c} production in e+e- and hadronic interactions

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    Predictions of the nonperturbative Quark Gluon Strings model based on the 1/N-expansion in QCD and string picture of interactions for production of states containing heavy quarks are considered. Relations between fragmentation functions for different states are used to predict the fragmentation function of c-quark to J/psi-mesons. The resulting cross section for J/psi-production in e+e- annihilation is in a good agreement with recent Belle result. It is argued that associated production of c\bar{c} states with open charm should give a substantial contribution to production of these states in hadronic interactions at very high energies.Comment: 7 pages, 2 figure

    Hadron Multiplicity in Lepton-Nucleon Interactions

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    Multi-hadron production in inelastic neutrino-nucleon interactions is investigated within the framework of the quark-gluon string model. The contributions of the planar (one-Reggeon exchange) and cylindrical (one-Pomeron exchange) graphs to different observables is computed using a Monte Carlo program for the generation of hadrons produced from the decay of colorless quark-antiquark strings. The suggested approach results in a satisfactory description of the experimental data on ν(νˉ)Nμ(μ+)hX\nu(\bar\nu) N\to\mu^-(\mu^+) h X reactions obtained recently at CERN by the NOMAD Collaboration. The data extends over a wide range of initial neutrino energies EνE_\nu << 200 GeV/c and momentum transfers 1 << Q << 7 GeV/c, well into the region where perturbative QCD calculations are not applicable.Comment: 10 pages, 5 figure

    Q2Q^2-dependence of backward pion multiplicity in neutrino-nucleus interactions

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    The production of pions emitted backward in inelastic neutrino-nucleus interactions is analyzed within the impulse approximation in the framework of the dual parton model. We focus on the Q2Q^2-dependence of the multiplicity of negative pions, normalized to the total cross section of the reaction ν+Aμ+X\nu + A \to \mu + X. The inclusion of planar (one-Reggeon exchange) and cylindrical (one-Pomeron exchange) graphs leads to a multiplicity that decreases as Q2Q^2 increases, in agreement with recent measurements carried out at CERN by the NOMAD collaboration. A realistic treatment of the high momentum tail of the nucleon distribution in a nucleus also allows for a satisfactory description of the semi-inclusive spectrum of backward pions.Comment: 15 pages, 4 figure

    Leading neutron spectra

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    It is shown that the observation of the spectra of leading neutrons from proton beams can be a good probe of absorptive and migration effects. We quantify how these effects modify the Reggeized pion-exchange description of the measurements of leading neutrons at HERA. We are able to obtain a satisfactory description of all the features of these data. We also briefly discuss the corresponding data for leading baryons produced in hadron-hadron collisions.Comment: 17 pages, 8 figures; sentence and reference added, reference corrected, to be published in EPJ

    Charmonium dissociation by mesons in heavy-ion collisions

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    The charmonium dissociation by mesons in relativistic heavy-ion reactions is analyzed within the Regge approach. It is shown that the inclusion of the initial and final state interactions in the dissociation of J/Psi to bar{D}* D* close to threshold increases the cross section significantly and can not be neglected in comparison to the total dissociation rate. This is due to resonant bar{D}*-D* interactions in sqrt{s} close to the masses of the Psi(4.04) and Psi(4.16) mesons. We also investigate thermal effects of the (c bar{c}) width for such processes in the medium. All these effects change both the magnitude and the shape of the cross section as a function of sqrt{s}. The results obtained should be applied in the analysis of open and hidden charm production in heavy-ion collisions.Comment: 4 pages, 2 figures; Talk given at ICTP 5th International Conference on Perspectives in Hadronic Physics, Trieste, Italy, 22-26 May 200
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