Oscillating neutrinos and μ→ e, γ

Abstract

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 largest Yakawa coupling is O(1) and 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. The work generalizes previous results of the literature, identifying the dominant contributions. 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 requirements. Other possible ways-out, like gauge mediated SUSY breaking, are also discussed.