Radiative and hadronic production of trimuons in neutrino collisions

We calculate characteristics of trimuon events in neutrino scattering, arising from conventional single-muon production accompanied by a dimuon pair from three sources: (i) radiation from the primary lepton-quark interaction, (ii) direct pair production from the subsequent hadronic interactions, deduced empirically from observed prompt muon-pair production in hadron-hadron collisions, and (iii) charm-pair production from the primary lepton-quark interaction. The first two components give a good representation of most of the ..nu..N ..-->.. ..mu../sup -/..mu../sup -/..mu../sup +/X data (the third component is small). A few trimuon events remain unexplained at muon-pair masses m (..mu../sup +/..mu../sup -/) > 1 GeV and at low hadronic energies. Same-sign dimuon and antineutrino trimuon predictions are also presented.