Space-time evolution and Hanbury Brown–Twiss analysis of relativistic heavy ion collisions in a chiral SU(3)×SU(3) model

The space-time dynamics and pion–Hanbury Brown–Twiss (HBT) radii in central heavy ion collisions at CERN-SPS and BNL-RHIC are investigated within a hydrodynamic simulation. The dependence of the dynamics and the HBT parameters on the equation of state (EOS) is studied with different parametrizations of a chiral SU(3) σ-ω model. The self-consistent collective expansion includes the effects of effective hadron masses, generated by the nonstrange and strange scalar condensates. Different chiral EOS show different types of phase transitions and even a crossover. The influence of the order of the phase transition and of the latent heat on the space-time dynamics and pion-HBT radii is studied. A small latent heat, i.e., a weak first-order chiral phase transition, or a smooth crossover lead to distinctly different HBT predictions than a strong first order phase transition. A quantitative description of the data, both at SPS energies as well as at RHIC energies, appears difficult to achieve within the ideal hydrodynamic approach using the SU(3) chiral EOS. A strong first-order quasiadiabatic chiral phase transition seems to be disfavored by the pion-HBT data from CERN-SPS and BNL-RHIC.