Abstract
Weak isosinglet Neutral Heavy Leptons (v m) have been searched for using data collected by the DELPHI detector corresponding to 3.3 × 106 hadronic Z0 decays at LEP1. Four separate searches have been performed, for short-lived v m production giving monojet or acollinear jet topologies, and for long-lived v m giving detectable secondary vertices or calorimeter clusters. No indication of the existence of these particles has been found, leading to an upper limit for the branching ratio BR(Z0 → v m?) of about 1.3 × 10−6 at 95% confidence level for v m masses between 3.5 and 50 GeV/c2. Outside this range the limit weakens rapidly with the v m mass. The results are also interpreted in terms of limits for the single production of excited neutrinos.
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A correction to this article is available at https://doi.org/10.1007/BF03546181
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DELPHI Collaboration. Search for neutral heavy leptons produced in Z decays. Z Phys C - Particles and Fields 74, 57–71 (1997). https://doi.org/10.1007/s002880050370
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DOI: https://doi.org/10.1007/s002880050370