70 research outputs found
A Multi-Phase Transport model for nuclear collisions at RHIC
To study heavy ion collisions at energies available from the Relativistic
Heavy Ion Collider, we have developed a multi-phase transport model that
includes both initial partonic and final hadronic interactions. Specifically,
the parton cascade model ZPC, which uses as input the parton distribution from
the HIJING model, is extended to include the quark-gluon to hadronic matter
transition and also final-state hadronic interactions based on the ART model.
Predictions of the model for central Au on Au collisions at RHIC are reported.Comment: 7 pages, 4 figure
Studying minijets via the dependence of two-particle correlation in azimuthal angle
Following my previous proposal that two-particle correlation functions can be
used to resolve the minijet contribution to particle production in minimum
biased events of high energy hadronic interactions, I study the and
energy dependence of the correlation. Using HIJING Monte Carlo model, it is
found that the correlation in azimuthal angle between
two particles with resembles much like two back-to-back jets as
increases at high colliding energies due to minijet production. It
is shown that , which is related to the relative fraction of
particles from minijets, increases with energy. The background of the
correlation for fixed also grows with energy due to the increase of
multiple minijet production. Application of this analysis to the study of jet
quenching in ultrarelativistic heavy ion collisions is also discussed.Comment: 11 pages Latex text and 8 ps figures, LBL-3349
Study of in-medium meson properties in Ap, pA and AA collisions
We propose to investigate the in-medium properties of vector mesons
at the normal nuclear density in Ap(pA) collisions and at higher density in AA
collisions at the ITEP accelerator facility TWAC. Using of the inverse Ap
kinematics will permit us to study the meson production in a wide
momentum interval included the not yet explored range of small meson momenta
relative to the projectile nuclei where the mass modification effect in nuclear
matter is expected to be the strongest. Momentum dependence of the in-medium
meson width will be studied in the traditional pA kinematics. We
intend to use the electromagnetic calorimeter for reconstruction of the
meson invariant mass by detecting photons from the decay. The model calculations and simulations with
RQMD generator show feasibility of the proposed experiment. Available now
intensity of the ion beams provides a possibility to collect large statistics
and make decisive conclusion about the meson properties at density of
normal nuclei. At the second stage of the investigation the meson
properties will be studied in AA collisions at higher density. Interpretation
of these measurements will be based on the results obtained in Ap(pA)
interactions. Further investigation of the in-medium properties of light
unflavored and charmed mesons can be performed at ITEP and at GSI(FAIR) where
higher ion energies will be accessible in near future.Comment: 26 pages, 10 figures, 2 table
Heavy Meson Production in Proton-Nucleus Reactions with Empirical Spectral Functions
We study the production of and mesons in reactions on the basis of empirical spectral functions. The high
momentum, high removal energy part of the spectral function is found to be
negligible in all cases close to the absolute threshold. Furthermore, the
two-step process () dominates the cross section at threshold energies in line with
earlier calculations based on the folding model.Comment: 18 pages, LaTeX, plus 14 postscript figures, submitted to Z. Phys.
Comparison of Experimental Data to the Relativistic Quantum Molecular Dynamics Model For Si+Au Collisions at 14.6 A GeV/c
Predictions from the RQMD model are systematically compared to recently
published charged hadron distributions of AGS Experiment 802 for central Si+Au
collisions at 14.6 GeV/, taking into account both the experimental
trigger condition and acceptance. The main features of the data, including
K production, can be understood quantitatively to better than 20\% within
the framework of the model, although several discrepancies are found, most
importantly for the proton spectra.Comment: 16 pages (TeX) plus 6 Postscript figures (tar-gz-compressed and
uuencoded
A Color Mutation Model of Soft Interaction in High Energy Hadronic Collisions
A comprehensive model, called ECOMB, is proposed to describe multiparticle
production by soft interaction. It incorporates the eikonal formalism, parton
model, color mutation, branching and recombination. The physics is conceptually
opposite to the dynamics that underlies the fragmentation of a string. The
partons are present initially in a hadronic collision; they form a single,
large, color-neutral cluster until color mutation of the quarks leads to a
fission of the cluster into two color-neutral subclusters. The mutation and
branching processes continue until only pairs are left in each small
cluster. The model contains self-similar dynamics and exhibits scaling behavior
in the factorial moments. It can satisfactorily reproduce the intermittency
data that no other model has been able to fit.Comment: 24 pages including 11 figures in revtex epsf styl
Simulation of Atmospheric Muon and Neutrino Fluxes with CORSIKA
The fluxes of atmospheric muons and neutrinos are calculated by a three
dimensional Monte Carlo simulation with the air shower code CORSIKA using the
hadronic interaction models DPMJET, VENUS, GHEISHA, and UrQMD. For the
simulation of low energy primary particles the original CORSIKA has been
extended by a parametrization of the solar modulation and a microscopic
calculation of the directional dependence of the geomagnetic cut-off functions.
An accurate description for the geography of the Earth has been included by a
digital elevation model, tables for the local magnetic field in the atmosphere,
and various atmospheric models for different geographic latitudes and annual
seasons. CORSIKA is used to calculate atmospheric muon fluxes for different
locations and the neutrino fluxes for Kamioka. The results of CORSIKA for the
muon fluxes are verified by an extensive comparison with recent measurements.
The obtained neutrino fluxes are compared with other calculations and the
influence of the hadronic interaction model, the geomagnetic cut-off and the
local magnetic field on the neutrino fluxes is investigated.Comment: revtex, 19 pages, 19 Postscript figures, submitted to Phys. Rev.
Hadronic observables from SIS to SPS energies - anything strange with strangeness ?
We calculate and (+) rapidity
distributions and compare to experimental data from SIS to SPS energies within
the UrQMD and HSD transport approaches that are both based on string, quark,
diquark () and hadronic degrees of freedom. The
two transport models do not include any explicit phase transition to a
quark-gluon plasma (QGP). It is found that both approaches agree rather well
with each other and with the experimental rapidity distributions for protons,
's, and . Inspite of this apparent agreement both
transport models fail to reproduce the maximum in the excitation function for
the ratio found experimentally between 11 and 40 AGeV. A
comparison to the various experimental data shows that this 'failure' is
dominantly due to an insufficient description of pion rapidity distributions
rather than missing 'strangeness'. The modest differences in the transport
model results -- on the other hand -- can be attributed to different
implementations of string formation and fragmentation, that are not
sufficiently controlled by experimental data for the 'elementary' reactions in
vacuum.Comment: 46 pages, including 15 eps figures, to be published in Phys. Rev.
Strangeness Enhancement in and Interactions at SPS Energies
The systematics of strangeness enhancement is calculated using the HIJING and
VENUS models and compared to recent data on , and
collisions at CERN/SPS energies (). The HIJING model is used to
perform a {\em linear} extrapolation from to . VENUS is used to
estimate the effects of final state cascading and possible non-conventional
production mechanisms. This comparison shows that the large enhancement of
strangeness observed in collisions, interpreted previously as possible
evidence for quark-gluon plasma formation, has its origins in non-equilibrium
dynamics of few nucleon systems. % Strangeness enhancement %is therefore traced
back to the change in the production dynamics %from to minimum bias
and central collisions. A factor of two enhancement of at
mid-rapidity is indicated by recent data, where on the average {\em one}
projectile nucleon interacts with only {\em two} target nucleons. There appears
to be another factor of two enhancement in the light ion reaction relative
to , when on the average only two projectile nucleons interact with two
target ones.Comment: 29 pages, 8 figures in uuencoded postscript fil
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