Searches for lepton-flavour violation

Abstract
Lepton-flavour violation is an important topic in particle physics, nowadays. The standard model, which describes jointly the electromagnetic and weak interactions, strictly conserves lepton flavour. On the other hand, most extensions of the standard model violate lepton-flavour conservation at some level. The article starts with definitions and gives a brief account of the standard model and its possible extensions. The experimental situation is reviewed in connection with the various theoretical predictions. The role of lepton-flavour violation in the search for physics beyond the standard model is emphasized.