Charged lepton flavor violation from massive neutrinos in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Z</mml:mi></mml:math>decays

Abstract

The present evidence for neutrino masses and lepton flavor mixings allows us to predict, in the standard model with light neutrinos, the branching rates for the decays $\stackrel{\ensuremath{\rightarrow}}{Z}e\ensuremath{\mu},$ \ensuremath{\mu}\ensuremath{\tau}, $e\ensuremath{\tau}$ of less than ${10}^{\ensuremath{-}54},$ while present experimental exclusion limits from CERN LEP 1 are of the order of ${10}^{\ensuremath{-}5}.$ The GigaZ option of the TESLA Linear Collider project will extend the sensitivity down to about ${10}^{\ensuremath{-}8}.$ We study in a systematic way some minimal extensions of the standard model and show that GigaZ might well be sensitive to the rates predicted from these scenarios.