Primordial hadrosynthesis in the Little Bang

The present status of soft hadron production in high energy heavy-ion collisions is summarized. In spite of strong evidence for extensive dynamical evolution and collective expansion of the fireball before freeze-out I argue that its chemical composition is hardly changed by hadronic final state interactions. The measured hadron yields thus reflect the primordial conditions at hadronization. The observed production pattern is consistent with statistical hadronization at the Hagedorn temperature from a state of uncorrelated, color deconfined quarks and antiquarks, but requires non-trivial chemical evolution of the fireball in a prehadronic (presumably QGP) stage before hadron formation.Comment: 10 pages LaTeX, including 5 figures. Invited overview talk given at Quark Matter '99, Torino, Italy, May 10-15, 1999. To appear in Nucl. Phys.

The Little Bang: Searching for quark-gluon matter in relativistic heavy-ion collisions

I review the status of the search for quark-gluon plasma in relativistic heavy-ion collisions. The available data provide strong evidence for the "three pillars of the Little Bang model": strong radial expansion of the collision fireball with Hubble-like scaling, thermal hadron emission and primordial hadrosynthesis. It is argued that the initial state of the reaction zone exhibits features which cannot be understood with conventional hadronic dynamics, but are consistent with the formation of deconfined quark-gluon matter.Comment: 18 pages, including 11 figures. Invited talk given at the 7th International Conference on Nucleus-Nucleus Collisions (NN2000), Strasbourg, 3-7 July 2000, to appear in the Proceedings in Nucl. Phys. A (W. Noerenberg, D. Guerreau, and V. Metag, editors). Figure caption of Fig. 2 correcte

From SPS to RHIC: Breaking the Barrier to the Quark-Gluon Plasma

After 15 years of heavy-ion collision experiments at the AGS and SPS, the recent turn-on of RHIC has initiated a new stage of quark-gluon plasma studies. I review the evidence for deconfined quark-gluon matter at SPS energies and the recent confirmation of some of the key ideas by the new RHIC data. Measurements of the elliptic flow at RHIC provide strong evidence for efficient thermalization during the very early partonic collision stage, resulting in a well-developed quark-gluon plasma with almost ideal fluid-dynamical collective behaviour and a lifetime of several fm/c.Comment: LaTex 12 pages, including 6 figures. Opening talk at the Conference "QCD@work", Martinafranca (Bari), June 16-20, 200