J/$\psi$ and $\phi$ production from proton to Pb induced reactions at CERN SPS

A new set of results obtained by the NA50 experiment for the $J/\psi$ production at the CERN SPS is presented. Peripheral Pb-Pb collisions benefit from an improved setup, confirming the departure from ordinary production observed for the most central collisions, which has suggested the occurrence of a quark-gluon plasma formation. Improved comparative analyses of older data confirms the phi meson yield increase with centrality and between systems. The interest of the ratio phi / omega as a direct measurement of the strangeness increase is underlined. (19 refs)