A New Upper Limit on the Decay $η\to e^{+}e^{-}$

Abstract

We have searched for the rare decay of the eta meson $η\to e^{+}e^{-}$ using the CLEO II detector. The $η$&#39;s were produced in $e^{+}e^{-}$ collisions with 10 GeV center-of-mass energy at the Cornell Electron Storage Ring (CESR). We find with 90% confidence the upper limit on the branching fraction $B(η\to e^{+}e^{-}) < 7.7\times 10^{-5}$. The application of conventional elementary particle theory to this decay predicts a branching fraction of about $10^{-9}$.