$$\tau \rightarrow \mu \mu \mu $$ at a rate of one out of $$10^{14}$$ tau decays?
$$\tau \rightarrow \mu \mu \mu $$ at a rate of one out of $$10^{14}$$ tau decays?
We present in a full analytic form the partial widths for the lepton flavour violating decays $\mu^\pm \to e^\pm e^+ e^-$ and $\tau^\pm \to \ell^\pm \ell'^{+} \ell'^{-}$, with $\ell,\ell'=\mu,e$, mediated by neutrino oscillations in the one-loop diagrams. Compared to the first result by Petcov in [1], obtained in the zero …