A comprehensive description of multiple observables in heavy-ion collisions at SPS

Abstract

Combining and expanding on work from previous publications, a model for the evolution of ultrarelativistic heavy-ion collisions at the CERN SPS for 158 A GeV beam energy is presented. Based on the assumption of thermalization and a parametrization of the spacetime expansion of the produced matter, this model is able to describe a large set of observables including hadronic momentum spectra, correlations and abundancies, the emission of real photons, dilepton radiation and the suppression pattern of charmonia. Each of these obervables provides unique capabilities to study the reaction dynamics and taken together they form a strong and consistent picture of the evolving system. Based on the emission of hard photons, we argue that a strongly interacting, hot and dense system with temperatures above 250 MeV has to be created early in the reaction. Such a system is bound to be different from hadronic matter and likely to be a quark–gluon plasma, and we find that this assumption is in line with the subsequent evolution of the system that is reflected in other observables.