We examine the muonium ($\mu ^+e^-$)-antimuonium ($\mu ^-e^+$) system in the models which accomodate the dilepton gauge bosons, and study their contributions to the ground state hyperfine splitting in ``muonium''. We also consider the exotic muon decay $\mu ^+\to e^+ +\overline \nu _e +\nu _{ \mu}$ mediated by the dilepton gauge boson, and obtain a lower bound $(M_{ X^{ \pm }}/g_{ 3l})>550 \rm GeV$ at 90\% confidence level for the singly-charged dilepton mass using the unitarity relation of the Kobayashi-Maskawa matrix for the 3-family case.
Categories: hep-ph