6 research outputs found
Multiplicity fluctuations in relativistic nuclear collisions
Multiplicity distributions of hadrons produced in central nucleus-nucleus
collisions are studied within the hadron-resonance gas model in the large
volume limit. In the canonical ensemble conservation of three charges (baryon
number, electric charge, and strangeness) is enforced. In addition, in the
micro-canonical ensemble energy conservation is included. An analytical method
is used to account for resonance decays. Multiplicity distributions and scaled
variances for negatively charged hadrons are presented along the chemical
freeze-out line of central Pb+Pb (Au+Au) collisions from SIS to LHC energies.
Predictions obtained within different statistical ensembles are compared with
preliminary NA49 experimental results on central Pb+Pb collisions in the SPS
energy range. The measured fluctuations are significantly narrower than a
Poisson reference distribution, and clearly favor expectations for the
micro-canonical ensemble.Comment: 6 pages, 3 figure
Multiplicity fluctuations in relativistic nuclear collisions: statistical model versus experimental data
The multiplicity distributions of hadrons produced in central nucleus-nucleus
collisions are studied within the hadron-resonance gas model in the large
volume limit. The microscopic correlator method is used to enforce conservation
of three charges - baryon number, electric charge, and strangeness - in the
canonical ensemble. In addition, in the micro-canonical ensemble energy
conservation is included. An analytical method is used to account for resonance
decays. The multiplicity distributions and the scaled variances for negatively,
positively, and all charged hadrons are calculated along the chemical
freeze-out line of central Pb+Pb (Au+Au) collisions from SIS to LHC energies.
Predictions obtained within different statistical ensembles are compared with
the preliminary NA49 experimental results on central Pb+Pb collisions in the
SPS energy range. The measured fluctuations are significantly narrower than the
Poisson ones and clearly favor expectations for the micro-canonical ensemble.
Thus this is a first observation of the recently predicted suppression of the
multiplicity fluctuations in relativistic gases in the thermodynamical limit
due to conservation laws.Comment: 27 pages, 9 figures, corrected reference
Multiplicity Fluctuations in Hadron-Resonance Gas
The charged hadron multiplicity fluctuations are considered in the canonical
ensemble. The microscopic correlator method is extended to include three
conserved charges: baryon number, electric charge and strangeness. The
analytical formulae are presented that allow to include resonance decay
contributions to correlations and fluctuations. We make the predictions for the
scaled variances of negative, positive and all charged hadrons in the most
central Pb+Pb (Au+Au) collisions for different collision energies from SIS and
AGS to SPS and RHIC.Comment: 19 pages, 4 figure
Multiplicity Distributions in Canonical and Microcanonical Statistical Ensembles
The aim of this paper is to introduce a new technique for calculation of
observables, in particular multiplicity distributions, in various statistical
ensembles at finite volume. The method is based on Fourier analysis of the
grand canonical partition function. Taylor expansion of the generating function
is used to separate contributions to the partition function in their power in
volume. We employ Laplace's asymptotic expansion to show that any equilibrium
distribution of multiplicity, charge, energy, etc. tends to a multivariate
normal distribution in the thermodynamic limit. Gram-Charlier expansion allows
additionally for calculation of finite volume corrections. Analytical formulas
are presented for inclusion of resonance decay and finite acceptance effects
directly into the system partition function. This paper consolidates and
extends previously published results of current investigation into properties
of statistical ensembles.Comment: 53 pages, 7 figure