Eur. Phys. J. C (2007) 51: 135-148
https://doi.org/10.1140/epjc/s10052-007-0281-z

Regular Article - Theoretical Physics

The Gibbs equilibrium conditions applied to the QGP–hadron transition curve

Physics Department, Nuclear and Particle Physics Section, University of Athens, Panepistimioupolis, Ilissia, 15771, Athens, Greece

^* e-mail: akapog@phys.uoa.gr

Received: 18 April 2006
Revised: 17 November 2006
Published online: 1 June 2007

Abstract

A method is developed to consistently satisfy the Gibbs equilibrium conditions between the quark–gluon and hadronic phase, although each phase has been formulated in separate grand canonical partition functions containing three quark flavours. The sector in the space of thermodynamic variables where the transition takes place is restricted to a curve, according to the phase diagram of QCD. The conservation laws of quantum numbers are also imposed on the transition curve. The effect of the inclusion of the pentaquark states is considered. The data from S+S, S+Ag (SPS) and Au+Au (RHIC) are found to be compatible with the formation of a QGP phase and the occurrence of the chemical freeze-out immediately after crossing the transition line, but the data from Pb+Pb (SPS) are not.