Bochum 2009 – scientific programme

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HK: Fachverband Hadronen und Kerne

HK 3: Heavy Ion Collisions and QCD phases

HK 3.2: Group Report

Monday, March 16, 2009, 14:30–15:00, H-ZO 10

Equation of state of the QGP in a virial expansion — •Stefano Mattiello and Wolfgang Cassing — Institut für Theoretische Physik, Universität Giessen, Germany

Recent observations at the Relativistic Heavy-Ion Collider indicate that the quark gluon plasma (QGP) created in ultrarelativistic Au + Au collisions is interacting more strongly than hadronic matter. To relax the approximation of the QGP as an ideal gas we use a generalised version of the classical virial expansion for µ_q=0 to calculate the partition function with a potential extracted from lattice calculations. We can describe three-flavour QCD lattice data with almost physical masses for the pressure, speed of sound and interaction measure at nonzero temperature and vanishing chemical potential. For the deconfined phase we use a phenomenological model which includes non-perturbative effects from dimension two gluon condensates that describe the free energy of quenched QCD very well. The hadronic phase is parametrised by a generalised resonance-gas model. Therefore, we extend this approach to finite densities introducing an explicit µ-dependence of the interaction. We calculate pressure, quark-number density, entropy and energy density and compare the results with lattice calculations. We, furthermore, investigate the structure of the phase diagram by calculating the isobaric and isentropic lines.
Work supported by DFG.