Iem-ft-211/01 Outp-01-11p

If neutrino masses and mixings are suitable to explain the atmospheric and solar neutrino fluxes, this amounts to contributions to FCNC processes, in particular μ → e, γ. If the theory is supersymmetric and the origin of the masses is a see-saw mechanism, we show that the prediction for BR(μ → e, γ) is in general larger than the experimental upper bound, especially if the solar data are explained by a large angle MSW effect, which recent analyses suggest as the preferred scenario. Our analysis is bottom-up and completely general, i.e. it is based just on observable low-energy data. Application of the results to scenarios with approximate top-neutrino unification, like SO(10) models, rules out most of them unless the leptonic Yukawa matrices satisfy very precise (fine-tuned) requirements. Other possible ways-out, like gauge mediated SUSY breaking, are also discussed. The work generalizes previous results of the literature, finding new (and dominant) contributions. March 2001 IEM-FT-211/01 OUTP-01-11P IFT-UAM/CSIC-01-08 hep-ph/0103065 E-mail: [email protected] E-mail: [email protected]