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 $<\approx 5$) 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 T, ${\mu }_q$ plane into the ${\mu }_s$-sector. Strangeness to baryon ratios f_s=1-2 prevail during a considerable fraction (50%) of the time evolution (i.e. $\Lambda$-droplets or even ${\Xi }^{-}$-droplets form the system at the late stage: The possibility of observing this time evolution via HBT correlations is discussed). The observed hadron ratios require $T_c\approx 160MeV$ and $B^{1/4}>\approx 200MeV$. If the present model is fit to the extrapolated hadron yields, metastable hypermatter can only be produced with a probability $p<10^{-8}$ for $A\ge 4$.

Comments: Submitted to Z. Phys. C