QCD Critical Point in a Quasiparticle Model

TL;DR

This paper models the QCD phase diagram using a quasiparticle approach for the quark-gluon plasma and an excluded volume model for hadron gas, identifying a critical end point near the chemical freeze-out curve relevant for RHIC experiments.

Contribution

It introduces a thermodynamically consistent quasiparticle model combined with an excluded volume hadron gas model to locate the QCD critical end point.

Findings

The phase transition line ends at a critical point (CEP).

The CEP is close to the chemical freeze-out curve.

The CEP is within the experimental reach of RHIC.

Abstract

Recent theoretical investigations have unveiled a rich structure in the quantum chromodynamics (QCD) phase diagram which consists of quark gluon plasma (QGP) and the hadronic phases but also supports the existence of a cross-over transition ending at a critical end point (CEP). We find a too large variation in determination of the coordinates of the CEP in the temperature (T), baryon chemical potential ($\mu_{B}$) plane and, therefore, its identification in the current heavy-ion experiments becomes debatable. Here we use an equation of state (EOS) for a deconfined QGP using a thermodynamically consistent quasiparticle model involving quarks and gluons having thermal masses. We further use a thermodynamically consistent excluded volume model for the hadron gas (HG) which was recently proposed by us. Using these equations of state, a first order deconfining phase transition is constructed using Gibbs' criteria. This leads to an interesting finding that the phase transition line ends at a critical point (CEP) beyond which a cross-over region exists. Using our thermal HG model, we obtain a chemical freeze out curve and we find that the CEP lies in close proximity to this curve as proposed by some authors. The coordinates of CEP are found to lie within the reach of RHIC experiment.