Observation of μ3π Events in e+e- Annihilation

We have observed events of the type μ^+/-+(3π)^-/+ in e⁺e^- interactions at center-of-mass energies above 6 GeV. The properties of the events are consistent with their coming from the heavy-lepton decays τ-->μνν¯ and τ¯-->ν¯3π or τ¯-->ν¯4π. The three-charged-pion invariant-mass distribution shows a significant peak at a mass 1.1 GeV/c². We find the branching ratio into three charged and any number of neutral pions B(τ⁺-->ν¯π⁺π⁺π^-nπ⁰)=0.18+/-0.065.