Statistical Hadronization and the Equation of State of the Quark Gluon Plasma * )

Statistical hadronization models are extremly succesful in describing measured ratios of hadrons produced in heavy-ion collisions for a wide range of beam energies from SIS to RHIC. Using the idea of statistical hadronization at the phase boundary within the framework of a recently proposed model for the thermodynamics of fireballs, we establish a relation between the equation of state (EoS) in the partonic phase probed at the phase transition temperature TC and the measured hadron ratios. In this way, the ratios can be predicted parameter-free. We demonstrate that this framework gives a consistent description of conditions both at SPS and RHIC. As the data on dilepton emission from heavy ion collisions give evidence for strong in-medium modifications of hadronic properties, we schematically investigate the sensitivity of our results to such modifications and qualitatively sketch a consistent scenario involving such in-medium effects.