Evidence for anomalous lepton production in e + e - annihilation

We have found events of the form e⁺+e^--->e^+/-+μ^-/++missing energy, in which no other charged particles or photons are detected. Most of these events are detected at or above a center-of-mass energy of 4 GeV. The missing-energy and missing-momentum spectra require that at least two additional particles be produced in each event. We have no conventional explanation for these events.