301 research outputs found
Fluctuations of Strangeness and Deconfinement Phase Transition in Nucleus-Nucleus Collisions
We suggest that the fluctuations of strange hadron multiplicity could be
sensitive to the equation of state and microscopic structure of strongly
interacting matter created at the early stage of high energy nucleus-nucleus
collisions. They may serve as an important tool in the study of the
deconfinement phase transition. We predict, within the statistical model of the
early stage, that the ratio of properly filtered fluctuations of strange to
non-strange hadron multiplicities should have a non-monotonic energy dependence
with a minimum in the mixed phase region.Comment: revised version to be published in Phys. Lett.
Comment on ``Strangeness enhancement in and S interactions at energies near 200 GeV"
We argue that the recent analysis of strangeness production in nuclear
collisions at 200 GeV/ performed by Topor Pop {\it et al.} \cite{To:95}
is flawed. The conclusions are based on an erroneous interpretation of the data
and the numerical model results. The term ``strangeness enhancement" is used in
a misleading way.Comment: 4 pages REVTEX 3.0, no figures; Comment submitted to Physical Review
Measures of Charge Fluctuations in Nuclear Collisions
The properties of two measures of charge fluctuations D and Delta Phi_q are
discussed within several toy models of nuclear collisions. In particular their
dependence on mean particle multiplicity, multiplicity fluctuations and net
electric charge are studied. It is shown that the measure Delta Phi_q is less
sensitive to these trivial biasing effects than the originally proposed measure
D. Furthermore the influence of resonance decay kinematics is analysed and it
is shown that it is likely to shadow a possible reduction of fluctuations due
to QGP creation.Comment: 9 pages, 9 figure
Transverse momentum versus multiplicity fluctuations in high-energy nuclear collisions
We discuss recently measured event-by-event fluctuations of transverse
momentum and of multiplicity in relativistic heavy-ion collisions. It is shown
that the non-monotonic behavior of the p_T-fluctuations as a function of
collision centrality can be fully explained by the observed non-monotonic
multiplicity fluctuations. A possible mechanism responsible for the
multiplicity fluctuations is also considered.Comment: 5 pages, 3 figures, revised & extended, to appear in Phys. Rev.
Fluctuations and Deconfinement Phase Transition in Nucleus-Nucleus Collisions
We propose a method to experimentally study the equation of state of strongly
interacting matter created at the early stage of nucleus--nucleus collisions.
The method exploits the relation between relative entropy and energy
fluctuations and equation of state. As a measurable quantity, the ratio of
properly filtered multiplicity to energy fluctuations is proposed. Within a
statistical approach to the early stage of nucleus-nucleus collisions, the
fluctuation ratio manifests a non--monotonic collision energy dependence with a
maximum in the domain where the onset of deconfinement occurs.Comment: revised version to be published in Phys. Lett.
Review of Results from the NA49 Collaboration
New results of the NA49 collaboration on strange particle production are
presented. Rapidity and transverse mass spectra as well as total multiplicities
are discussed. The study of their evolution from AGS over SPS to the highest
RHIC energy reveals a couple of interesting features. These include a sudden
change in the energy dependence of the mt-spectra and of the yields of strange
hadrons around 30 AGeV. Both are found to be difficult to be reproduced in a
hadronic scenario, but might be an indication for a phase transition to a quark
gluon plasma.Comment: 8 pages, 7 figures. Proceedings of the SQM04 conference, Capetow
Transverse Momentum Spectra of and Mesons from Quark Gluon Plasma Hadronization in Nuclear Collisions
Recent results on transverse mass spectra of and
mesons in central Pb+Pb collisions at 158 AGeV are considered. It is
shown that those results support a hypothesis of statistical production of
charmonia at hadronization and suggest the early thermal freeze--out of
and mesons. Based on this approach the collective
transverse velocity of hadronizing quark gluon plasma is estimated to be
. Predictions for transverse mass spectra of hidden and
open charm mesons at SPS and RHIC are discussed.Comment: Four pages, one figur
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
Particle Number Fluctuations in Canonical Ensemble
Fluctuations of charged particle number are studied in the canonical
ensemble. In the infinite volume limit the fluctuations in the canonical
ensemble are different from the fluctuations in the grand canonical one. Thus,
the well-known equivalence of both ensembles for the average quantities does
not extend for the fluctuations. In view of a possible relevance of the results
for the analysis of fluctuations in nuclear collisions at high energies, a role
of the limited kinematical acceptance is studied.Comment: 13 pages, 9 figures, LaTe
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