54 research outputs found
J/ suppression at 200 GeV in the comovers interaction model
The yield of per binary nucleon-nucleon collision in and
collisions at GeV is computed in the framework of the
dual parton model, supplemented with final state interaction (comovers
interaction). For the latter we use the same value of the cross-section,
mb, which describes the anomalous suppression
observed at CERN-SPS energies. Several possibilities for the value of the
absorptive cross-section are considered. Shadowing is introduced in both the
comovers and the yields. A comparison with the results at CERN-SPS,
including a prediction for collisions, is also presented.Comment: 15 pages, 3 figure
Strange baryon production asymmetry in K(+-)N interactions
The asymmetry of strange baryon production in Kp interactions at high
energies is considered in the framework of the Quark-Gluon String Model. The
contribution of the String-Junction Mechanism to the strange baryon production
is analysed.Comment: Contribution to the proceedings of the IV International Conference on
Quarks and Nuclear Physics (QNP06), Universidad Complutense, Madrid (Spain),
5-10 June 2006 (2 pages with 2 figures
Hard inclusive production and a violation of the factorization theorem
A new mechanism for hard inclusive production, which leads to a violation of
the factorization theorem, is suggested. The mechanism is illustrated by a
detailed discussion of Higgs meson production in high energy deutron-deutron
scattering. Numerical estimates for the effect are given for high energy hadron
(nucleus) scattering.Comment: 8 pages.latex,6 figures in ps file
The casuality and/or energy-momentum conservation constraints on QCD amplitudes in small x regime
The causality and/or the energy-momentum constraints on the amplitudes of
high energy processes are generalized to QCD. The constraints imply that the
energetic parton may experience at most one inelastic collision only and that
the number of the constituents in the light cone wave function of the
projectile is increasing with the collision energy and the atomic number.Comment: 24 pages,8 figures. The paper is streamlined, some references are
changed and misprints are eliminate
Microscopic Models of Heavy Ion Interactions
An introduction to dynamical microscopic models of hadronic and nuclear
interactions is presented. Special emphasis is put in the relation between
multiparticle production and total cross-section contributions. In heavy ion
collisions, some observables, considered as signals of the production of a
Quark Gluon Plasma (QGP), are studied. It is shown that they can only be
described if final state interactions are introduced. It is argued that the
cross-sections required are too small to drive the system to thermal
equilibrium within the duration time of the final state interaction.Comment: 39 pages, 18 figures. Lectures at VIII Hispalensis International
Summer School, Seville (Spain), to be published by Springer Verla
Parton Densities in a Nucleon
In this paper we re-analyse the situation with the shadowing corrections (SC)
in QCD for the proton deep inelastic structure functions. We reconsider the
Glauber - Mueller approach for the SC in deep inelastic scattering (DIS) and
suggest a new nonlinear evolution equation. We argue that this equation solves
the problem of the SC in the wide kinematic region where \as \kappa = \as
\frac{3 \pi \as}{2 Q^2R^2} x G(x,Q^2) \leq 1. Using the new equation we
estimate the value of the SC which turn out to be essential in the gluon deep
inelastic structure function but rather small in . We claim that
the SC in is so large that the BFKL Pomeron is hidden under the SC
and cannot be seen even in such "hard" processes that have been proposed to
test it. We found that the gluon density is proportional to in the
region of very small . This result means that the gluon density does not
reach saturation in the region of applicability of the new evolution equation.
It should be confronted with the solution of the GLR equation which leads to
saturation.Comment: latex file 53 pages, 27 figures in eps file
Production of vector mesons by real and virtual photons at high energies
A model based on Reggeon field theory is used for the description of the
photo- and electroproduction of vector mesons ()
on the proton. Its main feature is the dependence of the Pomeron intercept on
the virtuality of the photon. The few parameters of the model were determined
by fitting the total cross sections for real and virtual photons on the proton.
This allows a parameter-free description of the energy dependence of vector
meson production. Very good agreement with the existing high energy data is
obtained.Comment: 6 pages and 3 figures included in a uuencoded fil
Charm Production in DPMJET
In this work, charm production in the {\sc dpmjet} hadronic jet simulation is
compared to experimental data. Since the major application of {\sc dpmjet} is
the simulation of cosmic ray-induced air showers, the version of the code
integrated in the CORSIKA simulation package has been used for the comparison.
Wherever necessary, adjustments have been made to improve agreement between
simulation and data. With the availability of new muon/neutrino detectors that
combine a large fiducial volume with large amounts of shielding, investigation
of prompt muons and neutrinos from cosmic ray interactions will be feasible for
the first time. Furthermore, above TeV charmed particle decay
becomes the dominant background for diffuse extraterrestrial neutrino flux
searches. A reliable method to simulate charm production in high-energy
proton-nucleon interactions is therefore required.Comment: 10 pages, to be published in JCA
A momentum Space Analysis of the Triple Pomeron Vertex in pQCD
We study properties of the momentum space Triple Pomeron Vertex in
perturbative QCD. Particular attention is given to the collinear limit where
transverse momenta on one side of the vertex are much larger than on the other
side. We also comment on the kernels in nonlinear evolution equations.Comment: Minor misprints corrected. To be published in EPJ
The lepton pair production in heavy ion collisions in perturbation theory
We derive the first terms in the amplitude of lepton pair production in the
Coulomb fields of two relativistic heavy ions. Using the Sudakov technique,
which very simplify the calculations in momentum space for the processes at
high energies, we get the compact analytical expressions for differential cross
section of the process under consideration in the lowest order in fine
structure constant (Born approximation) valid for any momentum transfer and in
a wide kinematics region for produced particles. Exploiting the same technique
we consider the next terms of perturbation series (up to fourth order in fine
structure constant) and investigate their energy dependence and limiting cases.
It has been shown that taking in account all relevant terms in corresponding
order one obtains the expressions which are gauge invariant and finite. We
estimate the contribution of the Coulomb corrections to the total cross section
and discuss the cancellations of the different terms which holds in the total
cross section.Comment: LaTeX2e, 18 pages, 4 eps figure
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