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Advances in High Energy Physics
Volume 2013 (2013), Article ID 574871, 22 pages
Research Article

On the Higher Moments of Particle Multiplicity, Chemical Freeze-Out, and QCD Critical Endpoint

1Egyptian Center for Theoretical Physics (ECTP), MTI University, Cairo 11571, Egypt
2Research Center for Einstein Physics, Freie-University Berlin, Berlin, Germany

Received 6 January 2013; Revised 11 May 2013; Accepted 2 June 2013

Academic Editor: Edward Sarkisyan-Grinbaum

Copyright © 2013 A. Tawfik. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We calculate the first six nonnormalized moments of particle multiplicity within the framework of the hadron resonance gas model. In terms of the lower order moments and corresponding correlation functions, general expressions of higher order moments are derived. Thermal evolution of the first four normalized moments and their products (ratios) are studied at different chemical potentials, so that it is possible to evaluate them at chemical freeze-out curve. It is found that a nonmonotonic behaviour reflecting the dynamical fluctuation and strong correlation of particles starts to appear from the normalized third order moment. We introduce novel conditions for describing the chemical freeze-out curve. Although the hadron resonance gas model does not contain any information on the criticality related to the chiral dynamics and singularity in the physical observables, we are able to find out the location of the QCD critical endpoint at  MeV and temperature  MeV.