Dimuon events at the CERN pp-bar Collider

The observation of muon pairs with masses below the Z0 mass is reported in data from the 1983 and 1984 CERN pp-bar Collider runs. Sixty-seven events are observed for an integrated luminosity of 378 nb/sup -1/, requiring p/sub T/ > 3 GeV/c for each muon, and p/sub T/(μ/sub 1/) + p/sub T/(μ/sub 2/) > 10 GeV/c. The events are interpreted in terms of J/Psi and γ decays, the Drell-Yan mechanism, and heavy flavour processes. The observation of like-sign pairs of isolated muons is also reported. The authors are unable to explain these events in terms of the above processes