Strangeness enhancement at mid-rapidity in Pb-Pb collisions at 158 A GeV/ c

KS0, Λ, Ξ, Ω and negative particle h− yields and transverse mass spectra, measured at central rapidity in p-Pb and Pb-Pb collisions at 158 A GeV/c, are presented and discussed. Yields are studied as a function of the number of nucleons participating in the collision Npart, which have been estimated using the Glauber model. From p-Pb to Pb-Pb collisions the particle yields per participant increase substantially. Such an enhancement is more pronounced for multiply strange particles, and reaches an order of magnitude for Ω. For a number of participants Npart > 100, however, all yields per participant appear to be constant.