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

Abstract

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 $B(\eta \to e^{+}{e}^{-})<7.7\times 10^{-5}$. The application of conventional elementary particle theory to this decay predicts a branching fraction of about $10^{-9}$.

14 page postscript file also available through http://w4.lns.cornell.edu/public/CLNS, submitted to Physical Review D

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