2,514 research outputs found
Centrality dependence of global variables in relativistic heavy ion collisions: Final data analysis in the framework of a statistical model
The global variables like the transverse energy at midrapidity, the charged
particle multiplicity at midrapidity and the total multiplicity of charged
particles are evaluated in the single-freeze-out statistical model for
different centrality bins at RHIC at and 200 GeV. Full
description of decays of hadron resonances is applied in these estimations. The
geometric parameters of the model are obtained from the fit to the final data
on the spectra. The predicted values of the global variables agree
qualitatively well with the experimental data. The centrality independence of
the total number of charged particles per participant pair has been also
reproduced.Comment: Revtex, 12 figures (included), 16 pages. This is the revised final
version accepted for publication in Physical Review C. The main difference
with the first version is that the geometric parameters of the model have
been fitted again with the use of the newer estimates of the statistical
parameters reported in Refs. [20,21] for the case of GeV.
Also because of the editorial reasons the title has been slightly change
Excitations of Bose-Einstein condensates in optical lattices
In this paper we examine the excitations observable in atoms confined in an
optical lattice around the superfluid-insulator transition. We use increases in
the number variance of atoms, subsequent to tilting the lattice as the primary
diagnostic of excitations in the lattice. We show that this locally determined
quantity should be a robust indicator of coherence changes in the atoms
observed in recent experiments. This was found to hold for commensurate or
non-commensurate fillings of the lattice, implying our results will hold for a
wide range of physical cases. Our results are in good agreement with the
quantitative factors of recent experiments. We do, howevers, find extra
features in the excitation spectra. The variation of the spectra with the
duration of the perturbation also turns out to be an interesting diagnostic of
atom dynamics.Comment: 6 pages, 7 figures, using Revtex4; changes to version 2: new data and
substantial revision of tex
Statistical Coalescence Model with Exact Charm Conservation
The statistical coalescence model for the production of open and hidden charm
is considered within the canonical ensemble formulation. The data for the J/psi
multiplicity in Pb+Pb collisions at 158 A GeV are used for the model prediction
of the open charm yield which has not yet been measured in these reactions.Comment: 7 pages, Late
Strange particle production at RHIC in a single-freeze-out model
Strange particle ratios and pT-spectra are calculated in a thermal model with
single freeze-out, previously used successfully to describe non-strange
particle production at RHIC. The model and the recently released data for phi,
Lambda, anti-Lambda, and K*(892) are in very satisfactory agreement, showing
that the thermal approach can be used to describe the strangeness production at
RHIC.Comment: We have added the comparison of the model predictions to the newly
released Lambda and K*(892) pT-spectra from STA
Possible production of exotic baryonia in relativistic heavy-ion collisions
Properties of a hypothetical baryonium with the quark content
(uds\ov{u}\ov{d}\ov{s}) are discussed. The MIT bag model predicts its mass to
be unexpectedly low, approximately 1210 MeV. Possible hadronic decay modes of
this state are analyzed. Ultrarelativistic heavy-ion collisions provide
favorable conditions for the formation of such particles from the baryon-free
quark-gluon plasma. We estimate multiplicities of such exotic baryonia on the
basis of a simple thermal model.Comment: 8 pages, 1 figur
SHARE: Statistical Hadronization with Resonances
SHARE is a collection of programs designed for the statistical analysis of
particle production in relativistic heavy-ion collisions. With the physical
input of intensive statistical parameters, it generates the ratios of particle
abundances. The program includes cascade decays of all confirmed resonances
from the Particle Data Tables. The complete treatment of these resonances has
been known to be a crucial factor behind the success of the statistical
approach. An optional feature implemented is a Breit--Wigner type distribution
for strong resonances. An interface for fitting the parameters of the model to
the experimental data is provided.Comment: Extended version submitted to Computer Physics Communications.
Program available on the web at
http://www.physics.arizona.edu/~torrieri/SHARE/share.htm
Hadron Spectra and QGP Hadronization in Au+Au Collisions at RHIC
The transverse mass spectra of Omega hyperons and phi mesons measured
recently by STAR Collaboration in Au+Au collisions at sqrt(s_NN) = 130 GeV are
described within a hydrodynamic model of the quark gluon plasma expansion and
hadronization. The flow parameters at the plasma hadronization extracted by
fitting these data are used to predict the transverse mass spectra of J/psi and
psi' mesons.Comment: 4 pages, 4 figures, Fig. 3 correcte
Particle Number Fluctuations in Relativistic Bose and Fermi Gases
Particle number fluctuations are studied in relativistic Bose and Fermi
gases. The calculations are done within both the grand canonical and canonical
ensemble. The fluctuations in the canonical ensemble are found to be different
from those in the grand canonical one. Effects of quantum statistics increase
in the grand canonical ensemble for large chemical potential. This is, however,
not the case in the canonical ensemble. In the limit of large charge density a
strongest difference between the grand canonical and canonical ensemble results
is observed.Comment: 13 pages, 6 figure
Comparison of Chemical Freeze-Out Criteria in Heavy-Ion Collisions
One of the most remarkable results to emerge from heavy-ion collisions over
the past two decades is the striking regularity shown by particle yields at all
energies. This has led to several very successful proposals describing particle
yields over a very wide range of beam energies, reaching from 1 A GeV up to 200
A GeV, using only one or two parameters. A systematic comparison of these
proposals is presented here. The conditions of fixed energy per particle,
baryon+anti-baryon density, normalized entropy density as well as percolation
model are investigated. The results are compared with the most recent chemical
freeze-out parameters obtained in the thermal-statistical analysis of particle
yields. The sensitivity and dependence of the results on parameters is analyzed
and discussed. It is shown that in the energy range above the top AGS energy,
within present accuracies, all chemical freeze-out criteria give a fairly good
description of the particle yields. However, the low energy heavy-ion data
favor the constant energy per particle as a unified condition of chemical
particle freeze-out. This condition also shows the weakest sensitivity on model
assumptions and parameters.Comment: 15 pages 7 figures uses revte
Particle Ratios, Equilibration, and the QCD Phase Boundary
We discuss the status of thermal model descriptions of particle ratios in
central nucleus-nucleus collisions at ultra-relativistic energy. An alternative
to the
``Cleymans-Redlich'' interpretation of the freeze-out trajectory is given in
terms of the total baryon density. Emphasis is placed on the relation between
the chemical equilibration parameters and the QCD phase boundary. Furthermore,
we trace the essential difference between thermal model analyses of data from
collisions between elementary particles and from heavy ion collisions as due to
a transition from local strangeness conservation to percolation of strangeness
over large volumes, as occurs naturally in a deconfined medium.
We also discuss predictions of the thermal model for composite particle
production.Comment: Contribution to SQM2001 Conference, submitted to J. Phys.
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