Measurement of the τ− → e−ggneντ branching ratio

Abstract The branching ratio of the τ − → e − ν e ν τ decay mode has been measured with the OPAL detector to be (17.78 ± 0.10 ±0.09)% where the first error is statistical and the second is systematic. The branching ratio, together with other measurements, has been used to test e — μ and μ — τ universality in the charged current weak interaction.