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

Leading charm production in reaction $\pi^- N \rightarrow DX$ is discussed.Three experiments at Fermilab and CERN have measured a rather large enhancement in production rate of leading $D^-$-mesons over nonleading $D^+$.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 $c\bar{c}$ 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

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 $pp$ collisions at LHC energies and on the charmed meson production in ${\bar p}p$ 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

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

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 $\nu(\bar\nu) N\to\mu^-(\mu^+) h X$ reactions obtained recently at CERN by the NOMAD Collaboration. The data extends over a wide range of initial neutrino energies $E_\nu$ $<$ 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

On the re-summation of enhanced Pomeron diagrams

Dominant contributions of enhanced Pomeron diagrams to elastic hadron-hadron scattering amplitude are re-summed to all orders. The formalism is applied to calculate total hadronic cross sections and elastic scattering slopes. An agreement with earlier results is obtained

Diffractive Dissociation in Deep Inelastic Scattering at HERA

The diffraction dissociation of virtual photons is considered in the framework of conventional Regge theory. It is shown that the recent HERA data on large rapidity gap events can be successfully described in terms of the Pomeron structure function. Using Regge factorization, the latter can be related to the deuteron structure function. The parameters which relate these two structure functions are determined from soft hadronic diffraction data. The size of the shadowing corrections at low x and large Q**2 is also obtained.Comment: 17 pages, TEX, preprint LPTHE Orsay 94-4

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

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 $Q^2$-dependence of the multiplicity of negative pions, normalized to the total cross section of the reaction $\nu + A \to \mu + X$. The inclusion of planar (one-Reggeon exchange) and cylindrical (one-Pomeron exchange) graphs leads to a multiplicity that decreases as $Q^2$ 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

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