Muonium Hyperfine Structure and the Decay $ μ^+\to e^+ +\overline ν_e +ν_μ$ in Models with Dilepton Gauge Bosons

We examine the muonium ($μ^+e^-$)-antimuonium ($μ^-e^+$) 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 $μ^+\to e^+ +\overline ν_e +ν_μ$ 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.