Upper limits on the branching ratios τ → μγ and τ → eγ

The DELPHI collaboration has searched for lepton flavour violating decays τ → μγ and τ → eγ using a data sample of about 70 pb -1 of integrated luminosity corresponding to 81 000 produced τ +τ - events. No candidates were found for either of the two modes. This yields branching ratio upper limits of B(τ → eγ) < 1.1 × 10 -4 and B(τ → μγ) < 6.2 × 10 -5 at 90% confidence level.