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Bounds on extra quark-lepton generations from precision measurements

M. Maltoni

hep-pharXiv:hep-ph/0003314

Abstract

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 deltam around 1 GeV.

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