Strange particle production in 158 and 40 A GeV/c Pb-Pb and p-Be collisions

NA57 is an SPS experiment designed to study the energy and centrality
dependence of hyperon production in proton-nucleus and nucleus-nucleus
collisions. In this contribution, I report on the study of strangeness
enhancements as a function of collision centrality, both for 158 and 40 A
GeV/c beam momentum collisions.