A bilepton is a hypothetical particle predicted by the minimal 331 model. It is a spin one gauge boson which appears with single and double electric charge and with lepton number L=+2 and L=-2. It can mediate exotic processes such as V+A muon decay and muonium-antimuonium conversion. It can also give rise to exotic scattering processes such as electron plus electron goes to muon plus muon which is forbidden in the Standard Model. Detailed measurements made at the Paul Scherrer Institute (PSI) have searched for the exotic muon decay and placed a lower bound on the bilepton mass of about 1 TeV. Studies of muonium-antimuonium conversion, also at PSI, have imposed a similar bound. Higher statistics experiments are planned. The bilepton could alternatively be discovered in electron-electron collisions or in multi TeV proton-proton collisions at the Large Hadron Collider.
This particle was at first misnamed "dilepton", with a different pre-existing usage; the present name was introduced in 1996.