J/psi production in Indium-Indium collisions at 158 GeV/nucleon

Understand

The NA60 experiment studies muon pair production at the CERN SPS.

• In this letter we report on a precision measurement of J/psi in In-In collisions.
• We have studied the J/psi centrality distribution, and we have compared it with the one expected if absorption in cold nuclear matter were the only active suppression mechanism.
• For collisions involving more than ~80 participant nucleons, we find that an extra suppression is present.