Charged lepton flavor violation from massive neutrinos inZdecays

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 $\overrightarrow{Z}e\mu ,$ μτ, $e\tau$ of less than ${10}^{-54},$ while present experimental exclusion limits from CERN LEP 1 are of the order of ${10}^{-5}.$ The GigaZ option of the TESLA Linear Collider project will extend the sensitivity down to about ${10}^{-8}.$ 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.