Multimuon production by muons

We evaluate and compare the predictions of the principal mechanisms that are expected to produce multimuon signals $\mu N\to \left(n\mu \right)X$, namely (i) $\mu \overline{\mu }$ pair formation by bremsstrahlung and by photon-photon interaction, (ii) $c\overline{c}$ and $b\overline{b}$ heavy-quark production by photon-gluon fusion, and (iii) muon production by hadronic final-state interactions. We concentrate attention mainly on trimuons, but include some discussion of opposite-sign and same-sign dimuons, wrong-sign single muons, and diffractive $\psi$ production.