696 research outputs found
Fluctuations in statistical models
Proceedings of 4th International Workshop "Critical Point and Onset of Deconfinement", July 9-13, 2007, Darmstadt, Germany: The multiplicity fluctuations of hadrons are studied within the statistical hadron-resonance gas model in the large volume limit. The role of quantum statistics and resonance decay effects are discussed. 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 and positively charged hadrons are calculated for the sets of thermodynamical parameters 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
Quark-Gluon Plasma Signatures in Nucleus--Nucleus Collisions at CERN SPS
Two signatures of the quark-gluon plasma -- strangeness `enhancement' and
`suppression' -- in nucleus--nucleus collisions at the SPS energies
are critically discussed.Comment: Invited Talk at Symposium on Fundamental Issues in Elementary Matter,
In Honor and Memory of Michael Danos, Bad Honnef, Germany, 25-29 September
2000 (to be published in Heavy Ion Physics) Ref. [6] is correcte
Statistical Ensembles with Fluctuating Extensive Quantities
We suggest an extension of the standard concept of statistical ensembles.
Namely, we introduce a class of ensembles with extensive quantities fluctuating
according to an externally given distribution. As an example the influence of
energy fluctuations on multiplicity fluctuations in limited segments of
momentum space for a classical ultra-relativistic gas is considered.Comment: 4 pages, 2 figure
Thermodynamical Consistency of Excluded Volume Hadron Gas Models
The new excluded volume hadron gas model by Singh et al. [1-7] is critically
discussed. We demonstrate that in this model the results obtained from
relations between thermodynamical quantities disagree with the corresponding
results obtained by statistical ensemble averaging. Thus, the model does not
satisfy the requirements of thermodynamical consistency
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