A search for lepton flavour violating Z0 decays

We have searched for lepton flavour violating Z0→eμ, Z0→eτ and Z0→μτ decays in a sample of 4.0×106 visible Z0 decays collected with the OPAL detector at LEP during 1991 to 1994. No candidates are found for Z0→eμ. The samples of selected Z0→eτ and Z0→μτ candidates are consistent with the expected background. The following limits are set at 95% confidence level:$$\begin{gathered} BR(Z^0 \to e\mu ){\text{ }}< {\text{ 1}}{\text{.7 }} \times {\text{ 10}}^{ - {\text{6}}} \hfill \\ BR(Z^0 \to e\tau ){\text{ }}< {\text{ 9}}{\text{.8 }} \times {\text{ 10}}^{ - {\text{6}}} \hfill \\ BR(Z^0 \to \mu \tau ){\text{ }}< {\text{ 17}}{\text{. }} \times {\text{ 10}}^{ - {\text{6}}} . \hfill \\ \end{gathered}$$