Evidence for coexistence of two phases in relativistic heavy ion collisions and comparison with lattice results

The combined CERN and Brookhaven heavy ion (H.I) data supports a scenario of hadron gas which is in chemical and thermal equilibrium at a temperature T of about 140 MeV. Using the Brown-Stachel-Welke model (which gives 150 MeV). It is shown that in this scenario, the hot nucleons have mass 3 πT and the π and ρ mesons have masses close to πT and 2πT. This provides a possible connection with Euclidean time lattice masses of quarks. A simple model with pions and quarks supports the co-existence of two phases in these heavy ion experiments, suggesting a second order phase transition. (author)