Decayμ→eγin models with neutral heavy leptons

We explore possible muon-number-nonconserving processes in gauge theories in which the right-handed muon and electron appear along with neutral heavy leptons in $\mathrm{SU}\mathrm{}\left(2\right)\mathrm{}\otimes \mathrm{U}\mathrm{}\left(1\right)\mathrm{}$ doublets. The same mechanism which gives a mass to the electron and muon is expected to mix the left-handed neutral leptons with the neutrinos. In the simplest case, this leads to a rate for $\mu \to e\gamma$ 25 times larger than previously calculated in such models. Other phenomenological consequences of these theories are discussed. Formulas are given for the magnetic dipole transition matrix element in general gauge theories, and these are used to derive general conditions for suppression of $\mu \to e\gamma$ to acceptable levels.