Origin of trimuon events in high‐energy neutrino interactions

The properties of 76 neutrino‐initiated μ−μ−μ+ events observed in the CDHS detector in the 350 GeV and 400 GeV wide‐band beams at the CERN SPS are discussed. For neutrino energies ≳30 GeV and muon momenta ≳4.5 GeV, the average trimuon rate is (3.0±0.4) ×10−5 of the single‐muon event rate. The data are in agreement with normal charged‐current interactions with the additional production of a muon pair by both hadronic and radiative processes. No evidence is found for either heavy‐lepton or heavy‐quark cascades. Upper limits for these two possibilities are established.