New upper limit on the decay $\eta \to e^{+}{e}^{-}$

We have searched for the rare decay of the $\eta$ meson $\eta \to e^{+}{e}^{-}$ using the CLEO II detector. The $\eta$’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 $B(\eta \to e^{+}{e}^{-})<\mathrm{}7.7\mathrm{}\times {10}^{-5}$. The application of conventional elementary particle theory to this decay predicts a branching fraction of about ${10}^{-9}$.