FORMATION TIME OF HADRONS AND DENSITY OF MATTER PRODUCED IN RELATIVISTIC HEAVY-ION COLLISIONS

Density of matter produced in relativistic heavy-ion collisions depend s substantially on the space-time evolution of the collision and on th e Formation time of hadrons produced. Interactions of hadrons younger than their formation time are attenuated with respect to their normal values (transparency of hadronic matter for newly formed hadrons). The system of secondary hadrons produced in a heavy-ion collision thus ex pands as a gas of almost non interacting particles before hadrons reac h their formation time. Densities of interacting hadronic matter produ ced in oxygen-lead and sulphur-lead collisions at 200 GeV/nucleon are estimated as a function of the formation time of hadrons. Uncertaintie s in our knowledge of the critical temperature T-c and of the Formatio n time of hadrons tau(0) permit at present three scenarios: an optimis tic one (QGP has already been produced in collisions of oxygen and sul phur with heavy ions and will be copiously produced in Lead collisions ), a pessimistic one (QGP cannot be produced al 300 GeV/nucleon) and a n intermediate one (QGP has not been produced in oxygen and sulphur in teractions with heavy ions and will be at best produced only marginall y in Pb-coliisions). We find the last opinion as most probable.