84 research outputs found
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 collisions at LHC energies and on the
charmed meson production in 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
Hadron Multiplicity in Semi-Inclusive Lepton-Nucleon and Lepton-Nucleus Scattering
We discuss multi-hadron production in both inelastic neutrino-nucleon
interactions in the current fragmentation region and neutrino-nucleus
collisions in the target fragmentation region. Our analysis, carried out within
the framework of the quark-gluon string model, is mainly focused on the
difference between these two processes. We show that the dependence of
hadron multiplicity in the current and target fragmentation regions is indeed
completely different. The study of inelastic scattering in the target
fragmentation region also provides new information on nuclear structure at
small distances. The results of the proposed approach are in satisfactory
agreement with the data recently obtained at CERN by the NOMAD Collaboration.Comment: Talk delivered a the Fourth International Conference on Perspectives
in Hadronic Physics (ICTP, Trieste, Italy, May 2003). To be published in the
Proceedings (EPJA
-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 -dependence of the multiplicity of
negative pions, normalized to the total cross section of the reaction . The inclusion of planar (one-Reggeon exchange) and cylindrical
(one-Pomeron exchange) graphs leads to a multiplicity that decreases as
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
Gluon distribution in proton at soft and hard pp collisions
We analyze the inclusive spectra of hadrons produced in collisions at
high energies in the mid-rapidity region within the soft QCD and perturbative
QCD assuming the possible creation of the soft gluons at low intrinsic
transverse momenta . From the best description of the LHC data we found
the parametrization of the unintegrated gluon distribution which at low
is different from the one obtained within the perturbative QCD.Comment: 10 pages, 5 figures. Talk given the 5th joint International HADRON
STRUCTURE '11 Conference (HS'11), Tatransk\'a Strba, Slovakia, June 27th -
July 1st, 201
Antiproton production in and collisions close to threshold
The production of antiprotons in collisions is investigated close to
threshold where experimental data about the total cross section are not
available. We analyze the latter reaction within the LUND string model for
inclusive production and within the framework of a one-boson exchange
model for the exclusive reaction . The application
of our new results to the analysis of subthreshold antiproton production in and collisions shows cross sections that are much lower than
expected before. Nevertheless, the comparison of experimental
differential cross sections from and is expected to provide
valuable information about a nonnucleonic component in the deuteron
wavefunction.Comment: 10 pages, LaTeX, plus 4 postscript figures, Phys. Lett. B, in pres
Charmonium dissociation by mesons in heavy-ion collisions
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
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
reactions obtained recently at CERN by the NOMAD Collaboration. The data
extends over a wide range of initial neutrino energies 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
Reanalysis of antiproton production in proton-nucleus and nucleus-nucleus reactions at subthreshold energies
We reanalyse the production of pairs in proton-nucleus and
nucleus-nucleus collisions employing novel elementary cross sections for
baryon-baryon and pion-baryon production channels based on a boson-exchange
model. In contrast to previous transport studies performed in the literature
the secondary pion induced channel is found to be most important in both p+A
and A+A collisions at subthreshold energies. A detailed comparison with the
experimental data available indicates that sizeable attractive
potentials in the order of - 100 to - 150 MeV at normal nuclear matter density
are needed to reproduce the size and shape of the experimental spectra.Comment: 25 pages, latex, including 15 ps-figures, UGI-97-21, submitted to
Nucl. Phys.
Open charm enhancement by secondary interactions in relativistic nucleus-nucleus collisions?
We calculate open charm production in reactions at SPS energies
within the HSD transport approach - which is based on string, quark, diquark
() and hadronic degrees of freedom - including
the production of open charm pairs from secondary 'meson'-'baryon' (or
quark-diquark and antiquark-diquark) collisions. It is argued that at collision
energies close to the pair threshold the dominant production
mechanism is related to the two body (or quasi two body) reactions . Estimates within the framework of
the Quark-Gluon String model suggest cross sections of a few for in the region of 1 GeV above threshold. The dynamical
transport calculations for at 160 AGeV indicate that the open
charm enhancement reported by the NA50 Collaboration might be due to such
secondary reaction mechanisms.Comment: 14 pages, LaTeX, including 5 postscript figures, submitted to Phys.
Lett.
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