QCD Equation of State in a Quasi-Particle Perspective

Marcus Bluhm

The isentropic equation of state of strongly interacting matter is of significant importance in the hydrodynamical description of heavy ion collisions. We construct the equation of state within our quasi-particle model relating pressure, energy density, baryon number density and susceptibilities in agreement with first principle evaluations, i. e. QCD lattice calculations of the Bielefeld-Swansea group and of Gavai and Gupta. In the quasi-particle model, the excitation spectrum of quasi-particles is based on an extension of HTL/HDL selfenergies of propagating quark and gluon modes. Although lattice results are restricted to rather large quark masses, a possible chiral extrapolation within our model is discussed. As an example, we examine the equation of state for small baryon number densities relevant for experiments at RHIC and LHC and study its impact on azimuthal anisotropy in heavy ion collisions. The inclusion of critical end point effects is also discussed.