Electron-Muon and Electron-Hadron Production ine+e−Collisions

Abstract

We observe anomalous $e\mu$ and $e$-hadron events in $e^{+}{e}^{-}$ collisions at SPEAR in an experiment that uses a lead-glass counter system to identify electrons. The anomalous events are observed in the two-charged-prong topology. Their properties are consistent with the production of a pair of heavy leptons in the reaction $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}$ with subsequent decays of ${\tau }^{\pm }$ into leptons and hadrons. Under the assumption that they come only from this source, we measure the branching ratios $B(\tau \to e{\nu }_e{\nu }_{\tau })=(22.4\mathrm{}\pm 5.5)\%$ and $B(\tau \to h+\mathrm{neutrals})=(45\mathrm{}\pm 19)\%$.