Like-sign muon-electron production by neutrinos: Key to trilepton mechanisms

The most promising explanations of $\nu N\to {\mu }^{-}{\mu }^{-}X$ and $\nu N\to {\mu }^{-}{e}^{-}X$ like-sign dilepton events are two classes of models that have recently been proposed to explain neutrino trimuon production: (i) cascade decay of a charged heavy lepton $M^{-}$, (ii) decay of a neutral heavy lepton $M^0$ together with semileptonic decay of a new quark $b$. These two classes predict quite different lepton energies for $\nu N\to {\mu }^{-}{e}^{-}X$ events. They also predict completely different charge topologies for antineutrino-produced trileptons and like-sign dileptons.