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Article
Report number CERN-PPE-96-195
Title Search for Neutral Heavy Leptons Produced in Z Decays
Author(s) DELPHI Collaboration  Mostrar todos los 554 autores
Affiliation (CERN)
Publication 1997
Imprint 18 Dec 1996
Number of pages 27
In: Z. Phys. C 74 (1997) 57-71
DOI 10.1007/s002880050370
Subject category Particle Physics - Experiment
Accelerator/Facility, Experiment CERN LEP ; DELPHI
Abstract Weak isosinglet Neutral Heavy Leptons (νm) 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 νm production giving monojet or acollinear jet topologies, and for long-lived νm 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(Z0νmν¯) of about 1.3×106 at 95\% confidence level for νm masses between 3.5 and 50 GeV/c2. Outside this range the limit weakens rapidly with the νm mass. %Special emphasis has been given to the search for monojet--like topologies. One event %has passed the selection, in agreement with the expectation from the reaction: %e+e¯νν¯. The results are also interpreted in terms of limits for the single production of excited neutrinos.

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