Bounds on Extra Quark-lepton Generations from Precision Measurements
نویسنده
چکیده
The existence of extra chiral generations is strongly disfavored by the precision electroweak data if all the extra fermions are heavier than mZ . However fits as good as the SM can be obtained if one allows the new neutral leptons to have masses close to 50 GeV. In the framework of SUSY models precision measurements cannot exclude one additional generation of heavy fermions if chargino and neutralino have masses around 60 GeV with ∆mχ̃±,0 ≃ 1 GeV.
منابع مشابه
26 1 v 1 2 4 Ju n 20 01 Precision measurements , extra quark - lepton generations and 50 GeV neutrinos
The existence of extra chiral generations with all fermions heavier than m Z is strongly disfavored by the precision electroweak data. However the data still allow a few extra generations if the neutral lep-tons have masses close to 50 GeV. Such heavy neutrino can be searched in the reaction e + e − → N ¯ N γ. Existence of 50 GeV neutrinos makes standard model Higgs boson invisible.
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