  The NA57 experiment at the CERN SPS has measured the production of strange
and multi-strange particles in Pb-Pb (and p-Be) collisions at mid-rapidity. The
collective dynamics of the collision is studied in the transverse and
longitudinal directions as a function of centrality and beam momentum and
analysed based on hydrodynamical models. Central-to-peripheral nuclear
modification factors at 158 A GeV/c are presented and compared with other
measurements and theory.

Nuclear Theory;Nuclear Experiment