and θ production from proton to Pb induced reactions at CERN SPS

Abstract A new set of results obtained by the NA50 experiment for the J/ψ 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 datas confirms the θ meson yield increase with centrality and between systems. The interest of the ratio θ ω as a direct measurement of the strangeness increase is underlined.