Experimental Study of Heavy Charged Leptons and Search for Scalar Partners of Muons at PETRA (12 GeV<~Ec.m.<~36.7 GeV)

Data from the MARK-J detector on the reactions e/sup +/e/sup -/..--> mu../sup +/..mu../sup -/,tau/sup +/tau/sup -/ in the center-of-mass energy range from 12 to 36.7 GeV are presented. The ..mu..,tau radii are shown to be <10/sup -16/ cm. A search has been made for the production of a new heavy lepton and for the production of spin-0 supersymmetric partners of the muon. 95%-confidence-level lower limits of 16 GeV for the mass of a new charged heavy lepton and 15 GeV for the mass of the scalar partners of the muon are obtained.