First results on Quark Matter creation with nuclear collisions at the SPS.

Stock R.
Institut fuer Kernphysik, Universitaet Frankfurt/Main, D-60486 Frankfurt/Main

Systematic and comprehensive data are now available from the SPS Lead ( Pb 208) beam program. Its goal was to ascertain the Lattice QCD prediction of a deconfined continuous state of strongly interacting matter ( the so-called Quark - Gluon - Plasma ) setting in at extreme energy density. Central collisions Pb+Pb appear, first of all, to exceed the critical QCD energy density. Second, the data observed for J/Psi production suppression are consistent with the hypothesis that a plasma "fireball" was indeed created in the primordial phase of the collision dynamics. Third, this partonic phase would then have to expand, cool and reach the phase boundary for the decay back to hadrons. This boundary has indeed been located at temperature T=175+-10 MeV, baryochemical potential of about 250 MeV, and at an energy density of about 1 GeV/cubic fermi. The latter information stems from analysis of production ratios of all created hadronic species ranging from pions to Omega hyperons. This analysis is applicable down to single collision event as central Pb+Pb collisions produce about 2400 hadrons per event.

Presenting Author : Stock R.
Presentation : Oral