Flavour Violation in charged leptons: Present and Future

Abstract

In the absence of a fundamental principle preventing charged lepton flavour violation, one expects that extensions of the Standard Model accommodating neutrino masses and mixings should also allow for charged lepton flavour violating processes such as $\ell_i \to \ell_jγ$, $\ell_i \to \ell_j \ell_k \ell_m $ and $μ- e$ conversion in nuclei, for which the rates depend in general on the mechanism of neutrino mass generation. In addition to low-energy experiments, there are also searches for lepton flavour violation at colliders, where new physics can be directly probed through flavour violating production and/or decays of heavy states. In a model independent way, we briefly use effective operators responsible for these processes to derive information about the underlying framework of new physics. We then consider some specific classes of models (supersymmetry, extra dimensions, grand unified theories) that account for rich scenarios of charged lepton flavour violation. We also comment on the rôle of charged lepton flavour violation in disentangling models of new physics.