J/ ψ production in p-A collisions at 158 and 400 GeV: recent results from the NA60 experiment

Abstract

The NA60 experiment has studied muon pair production in p-A and In-In collisions at the CERN SPS. We present new results on nuclear effects on J/ ψ production in p-A at 158 GeV, the same energy used for collecting A-A data at the SPS. We then compare nuclear effects with previous results from fixed target experiments, and with the results obtained from a p-A data sample taken by NA60 at 400 GeV. Based on the 158 GeV results, we calculate the expected J/ ψ suppression in In-In and Pb-Pb collisions due to cold nuclear matter effects, and we extract a new estimate for the anomalous suppression at SPS energies. Finally, we show preliminary results on J/ ψ polarization in p-A collisions.