Constraints on muonium-antimuonium conversion

We discuss a simple model in which muonium-antimuonium conversion can occur at a level around the recent experimental bound but the process μ→eγ is strictly forbidden. Measurements of the anomalous muon magnetic moment and high-energy Bhabha scattering $e^{+}$ $e^{\mathrm{-}}$→$e^{+}$ $e^{\mathrm{-}}$ together provide an indirect and interesting constraint on the conversion. The model predicts anomalous events ep→ēμμX at high-energy ep colliders.