Evidence for ψψ production in π− interactions at 150 and 280 GeV/c

Abstract From the analysis of multimuon events produced by π − interactions at 150 and 280 GeV/ c in the NA3 spectrometer, we present evidence for the production of two J/ψ mesons in the same interaction (13 events seen, for an expected background of about 0.2 events). Some possible production mechanisms are described and an estimation of the cross section is given.