Search for exotic tau decays

Abstract The Crystal Ball detector at the Doris II storage ring at DESY was used to search for the exotic decay processes τ →e γ , τ →e π 0 , and τ →e η . No signal was observed. We obtained the following 90% CL upper limits on the branching fractions: B ( τ →e γ ) −4 , B ( τ →e π 0 ) −4 , B ( τ →e η ) −4 .