Unstable Charged Heavy Leptons Research Articles

Search for heavy neutral and charged leptons in e +e − annihilation at [formula omitted] = 183 and 189 GeV

A search for unstable neutral and charged heavy leptons as well as for stable charged heavy leptons is performed at center-of-mass energies s = 183 and 189 GeV with the L3 detector at LEP. No evidence for their existence is found. We exclude neutral heavy leptons which couple to the electron, muon or tau family, of the Dirac type for masses below 92.4, 93.3 and 83.3 GeV, and of the Majorana type for masses below 81.8, 84.1 and 73.5 GeV, respectively. We exclude unstable charged heavy leptons for masses below 93.9 GeV for a wide range of the associated neutral heavy lepton mass. If the unstable charged heavy lepton decays to a light neutrino, we exclude masses below 92.4 GeV. The production of stable charged heavy leptons with mass less than 93.5 GeV is also excluded.

Search for heavy neutral and charged leptons in e+e− annihilation at =161 = 172

Abstract A search for unstable neutral and charged heavy leptons as well as for stable charged heavy leptons has been made at center-of-mass energies s = 161 GeV and s 172 GeV with the L3 detector at LEP. No evidence for their existence was found. We exclude unstable neutral leptons of Dirac (Majorana) type for masses below 78.0 (66.7), 78.0 (66.7) and 72.2 (58.2) GeV, if the heavy neutrino couples to the electron, muon or tau family, respectively. We exclude unstable charged heavy leptons for masses below 81.0 GeV for a wide mass range of the associated neutral heavy lepton. The production of stable charged heavy leptons with a mass less than 84.2 GeV is also excluded. If the unstable charged heavy lepton decays via mixing into a massless neutrino, we exclude masses below 78.7 GeV.

Search for unstable sequential neutral and charged heavy leptons in e +e − annihilation at [formula omitted] and 136 GeV

A search for unstable sequential neutral and charged heavy leptons has been made at center-of-mass energies 130 and 136 GeV with the L3 detector at LEP. The neutral leptons are assumed to decay via mixing to electrons and muons. No evidence for their existence was found. We exclude unstable Dirac neutrinos for masses below 59.3 (57.9) GeV and unstable Majorana neutrinos below 48.6 (47.2) GeV if the neutrino couples to the electron(muon) family. We exclude unstable charged heavy leptons for masses below 61 GeV for a wide range of the associated neutral lepton mass.