Hadron production in relativistic nuclear collisions: Thermal hadron source or hadronizing quark-gluon plasma?

Abstract

Measured hadron yields from relativistic nuclear collisions can be equally well understood in two physically distinct models, namely a static thermal hadronic source vs. a time-dependent, nonequilibrium hadronization off a quark-gluon plasma droplet. Due to the time-dependent particle evaporation off the hadronic surface in the latter approach the hadron ratios change (by factors of less than and double approximate 5) in time. Final particle yields reflect time averages over the actual thermodynamic properties of the system at a certain stage of the evolution. Calculated hadron, strangelet and (anti-)cluster yields as well as freeze-out times are presented for different systems. Due to strangeness distillation the system moves rapidly out of the Τ, μq plane into the μs-sector. Strangeness to baryon ratios fs = 1 - 2 prevail during a considerable fraction (50%) of the time evolution (i.e. Λ-droplets or even Ξ--droplets form the system at the late stage: The possibility of observing this time evolution via two-particle correlations is discussed). The observed hadron ratios require Τc ≈ 160 MeV and B1/4 Greater than and approximate 200 MeV. If the present model is fit to the extrapolated hadron yields, metastable hypermatter can only be produced with a probability p < 10-8 for A ≥ 4.