Observation of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>μ</mml:mi><mml:mn>3</mml:mn><mml:mi>π</mml:mi></mml:math>Events in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>Annihilation

We have observed events of the type ${\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}+{(3\ensuremath{\pi})}^{\ensuremath{\mp}}$ in ${e}^{+}{e}^{\ensuremath{-}}$ interactions at center-of-mass energies above 6 GeV. The properties of the events are consistent with their coming from the heavy-lepton decays $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\nu}\overline{\ensuremath{\nu}}$ and $\overline{\ensuremath{\tau}}\ensuremath{\rightarrow}\overline{\ensuremath{\nu}}3\ensuremath{\pi}$ or $\overline{\ensuremath{\tau}}\ensuremath{\rightarrow}\overline{\ensuremath{\nu}}4\ensuremath{\pi}$. The three-charged-pion invariant-mass distribution shows a significant peak at a mass 1.1 GeV/${\mathit{c}}^{2}$. We find the branching ratio into three charged and any number of neutral pions $B({\ensuremath{\tau}}^{+}\ensuremath{\rightarrow}\overline{\ensuremath{\nu}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}n{\ensuremath{\pi}}^{0})=0.18\ifmmode\pm\else\textpm\fi{}0.065$.