Supersymmetric signals in muon and tau decays

The spectra of the decay leptons produced in μ and τ decays could be significantly different from the standard model predictions. Such changes can be induced by majoron emission processes, characteristic of supersymmetric (SUSY) SU(2) x U(1) models with spontaneously broken R-parity. We analyse the attainable values for the corresponding branching ratios, once all observational constraints have been incorporated, including both those that arise from collider experiments such as LEP, as well as weak interaction constraints, such as the non-observation of neutrinoless double β decay, the limits on the ντ mass, the non-observation of neutrino oscillations, etc. We conclude that a new generation of high luminosity experiments such as a τ factory could easily study these branching ratios, even if the ντ mass is below the attainable limit of sensitivity of the planned facilities. (orig.)