Isolated Leptons (5 muons and 1 electron)

in events with large missing transverse momentum

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	The isolated lepton events were found in positron-proton scattering processes. Their kinematic properties are shown as a function of  PtX: transverse momentum of the hadronic final state particles, and Mt: transverse mass calculated from the lepton and the missing transverse momentum vector. The circles indicate the luminosity equivalent of a 500 fold statistics for simulated events using photoproduction of W-Bosons, The triangles indicate the luminosity equivalent of a 500 fold statistics for simulated events using two-photon production of leptons.
The electron event is compatible with resulting from W-boson production. The 5 muon events observed cannot explained by the leading order calculation of W-production (0.53+/-0.11 events expected) or two-photon processes (0.14+0.14-0.07 events expected).  Three of the muon events are in a phase space region that is atypical for Standard Model processes.