14 research outputs found
Study of correlations at LHC and RHIC energies in collisions within the quark-gluon string model
The Quark Gluon String Model (QGSM) reproduces well the global
characteristics of the collisions at RHIC and LHC, e.g., the
pseudorapidity and transverse momenta distributions at different centralities.
The main goal of this work is to employ the Monte Carlo QGSM for description of
femtoscopic characteristics in collisions at RHIC and LHC. The study is
concentrated on the low multiplicity and multiplicity averaged events, where no
collective effects are expected. The different procedures for fitting the
one-dimensional correlation functions of pions are studied and compared with
the space-time distributions extracted directly from the model. Particularly,
it is shown that the double Gaussian fit reveals the contributions coming
separately from resonances and from directly produced particles. The comparison
of model results with the experimental data favors decrease of particle
formation time with rising collision energy.Comment: 9 pages, 14 figures, 2 table
Anisotropic flow of charged and identified hadrons in the quark-gluon string model for Au+Au collisions at sqrt(s) = 200 GeV
The pseudorapidity behaviour of the azimuthal anisotropy parameters v_1 and
v_2 of inclusive charged hadrons and their dependence on the centrality has
been studied in Au+Au collisions at full RHIC energy of sqrt(s) = 200 GeV
within the microscopic quark-gluon string model. The QGSM simulation results
for the directed flow v_1 show antiflow alignment within the pseudorapidity
range |eta| < 2 in a fair agreement with the experimental v_1(eta) data, but
cannot reproduce the further development of the antiflow up to |eta| around
3.5. The eta dependence of the elliptic flow v_2 extracted from the simulations
agrees well with the experimental data in the whole pseudorapidity range for
different centrality classes. The centrality dependence of the integrated
elliptic flow of charged hadrons in the QGSM almost coincides with the PHOBOS
experimental distribution. The transverse momentum dependence of the elliptic
flow of identified and inclusive charged hadrons is studied also. The model
reproduces quantitatively the low p_T part of the distributions rather good,
but underestimates the measured elliptic flow for transverse momenta p_T > 1
GeV/c. Qualitatively, however, the model is able to reproduce the saturation of
the v_2(p_T) spectra with rising p_T as well as the crossing of the elliptic
flow for mesons and baryons.Comment: REVTeX, 10 pages, 10 figures, v2: extended discussion of the model
results, accepted for publication in Phys. Rev.
Multiparton interactions and production of minijets in high energy hadronic collisions
We discuss the inclusive cross section to produce two minijets with a large
separation in rapidity in high energy hadronic collisions. The contribution to
the inclusive cross section from the exchange of a BFKL Pomeron is compared
with the contribution from the exchange of two BFKL Pomerons, which is induced
by the unitarization of the semi-hard interaction. The effect of the multiple
exchange is studied both as a function of the azimuthal correlation and as a
function of the transverse momentum of the observed minijets.Comment: TeX file, 20 pages, 4 figures available on reques
Cosmic Ray Air Shower Characteristics in the Framework of the Parton-Based Gribov-Regge Model NEXUS
The purpose of this paper is twofold: first we want to introduce a new type
of hadronic interaction model (NEXUS), which has a much more solid theoretical
basis as, for example, presently used models like QGSJET and VENUS, and ensures
therefore a much more reliable extrapolation towards high energies. Secondly,
we want to promote an extensive air shower (EAS) calculation scheme, based on
cascade equations rather than explicit Monte Carlo simulations, which is very
accurate in calculations of main EAS characteristics and extremely fast
concerning computing time. We employ the NEXUS model to provide the necessary
data on particle production in hadron-air collisions and present the average
EAS characteristics for energies 10^14 - 10^17 eV. The experimental data of the
casa-blanka group are analyzed in the framework of the new model.Comment: 15 pages, 8 figure
Multiparticle production in small-x deep inelastic scattering and the nature of the Pomeron
Properties of multiparticle final states produced in the central rapidity
region of small-x deep inelastic scattering (DIS) are discussed. It is pointed
out that these properties contain important information on the nature of the
Pomeron - used for the description of total cross section and diffractive
production in DIS. It is shown that models based on universality of the Pomeron
predict charged particle multiplicities in small-x DIS which are in good
agreement with recent HERA results.Comment: 14 pages, plain LaTeX + 4 LaTeX figures (feynman package is needed) +
6 PostScript figure
Minijets and the Two-Body Parton Correlation
A large number of double parton scatterings have been recently measured by
CDF. The double parton scattering process measures , a non
perturbative quantity related to the hadronic transverse size and with the
dimensions of a cross section. The actual value measured by CDF is considerably
smaller as compared with the naive expectation, namely the value of the
inelastic non diffractive cross section. The small value of may
be an effect of the hadron structure in transverse plane. We discuss the
problem by taking into account, at all orders, the two-body parton correlations
in the many-body parton distributions.Comment: 19 pages, plane tex, no figure