We present measurements of inclusive anomalous muon production in $e^{+}{e}^{-}$ annihilations in three energy ranges. In all three ranges we observe a large anomalous muon production rate in two-prong events which is compatible with the expected decays of pairs of heavy leptons. In the highest energy range there is also appreciable anomalous muon production in multiprong events which, due to its magnitude and momentum dependence, must come in part from a source other than a heavy lepton.

• Received 8 November 1976

DOI:https://doi.org/10.1103/PhysRevLett.38.117