Quark-Gluon-Plasma Formation at CERN-SPS Energies (200 GeV)?

By colliding ultrarelativistic ions, one achieves energy densities close to the critical value for the formation of a quark-gluon plasma. We introduce a percolation approach to model the final stage ($\tau >1\mathrm{}$ fm/c) of ion-ion collisions, the initial stage being treated by well-established methods, based on strings and Pomerons. The percolation approach amounts to finding high density domains, and treating them as quark-matter droplets. In this way, we have a realistic, microscopic, and Monte Carlo-based model which allows for the formation of quark matter. We find that even at CERN SPS energies large quark-matter droplets are formed—at a low rate though. Large quark-matter droplets are formed due to geometrical fluctuation, but not in the average event.