τ→μγ and μ→eγ as probes of neutrino mass models

We discuss the possibility of discriminating between different supersymmetric see-saw models by improving the experimental sensitivity to charged lepton flavour violating processes. Assuming a hierarchical neutrino mass spectrum, we classify see-saw models according to how the hierarchy Deltam(circle dot)(2) much less than Deltam(atm)(2) is generated, and study the predictions of each class for the branching ratios of tau --> mu gamma and mu --> e gamma. The process tau --> mu gamma is found to be a particularly promising tool to probe the fundamental seesaw parameters, and especially to identify the origin of the large atmospheric mixing angle. Predictions for mu --> e gamma are more model-dependent. We point out that, even with an improvement of the experimental sensitivities by three orders of magnitude, both tau --> mu gamma and mu --> e gamma could escape detection in models where Deltam(atm)(2) is determined by one of the lightest right-handed atm neutrinos. (C) 2001 Elsevier Science B.V. All rights reserved.