Abstract :
The CERN heavy ion program, started in 1986 with the oxigen beam, has accumulated an impressive amount of experimental results on the study of high energy density nuclear matter. Many experiments where devoted to the study of the lead-lead collisions at center of mass energy of about 20 GeV and all finally agreed in concluding that in the central lead-lead interactions a new state of matter as been created with many of the characteristics foreseen for the Quark-Gluon Plasma.
