Produzione di particelle strane in interazioni piombo-piombo e protone-piombo a 160 GeV/c per nucleone

This PhD thesis is about the production of strange particles in heavy-ion collisions at high energy produced at the SPS CERN syncrotron. Results are from experiment WA85 and WA97. They have been compared with VENUS and RQMD simulations. An increase in strangeness production has been observed which cannot be explained in terms of superposition of hadron-hadron collisions. It is in favour of a QGP scenario, developed in the early stages of the collisions