J/ψ and ψ′ production and their normal nuclear absorption in proton-nucleus collisions at 400∈GeV

We report a new measurement of J/ψ, ψ′ and Drell-Yan cross-sections, in the kinematical domain -0.425<y _cm<0.575 and -0.5<cosθ _CS<0.5, performed at the CERN-SPS using 400 GeV/c incident protons on Be, Al, Cu, Ag, W and Pb targets. The dependence of the charmonia production cross-sections on the size of the target nucleus allows to quantify the so-called normal nuclear absorption. In the framework of the Glauber model, this new measurement is combined with results previously obtained with the same apparatus, under different experimental conditions, and leads to a precise determination of the J/ψ and ψ′ absorption cross-sections in the surrounding nuclear matter.