CMS looks for evidence of J/ψ mesons in near-collision events in the LHC’s 2011 heavy-ion run, during which lead nuclei were accelerated to an unprecedented energy of 574 trillion electronvolts.

More than expected

CDF observes approximately 740 events in the muon decay mode. CDF looked for a signature of three muons, the mass of two oppositely charged muons being consistent with that of the J/ψ particle.