Evidence for DirectγProduction at Largexinψ(3100)Decay

Abstract

The inclusive $\gamma$ and ${\pi }^0$ momentum spectra from $\psi \mathrm{}\left(3100\right)\mathrm{}$ decay have been measured in $e^{+}{e}^{-}$ annihilation at SPEAR. When the $\gamma$ spectrum is compared with that expected from ${\pi }^0$ decay, an excess of high-momentum $\gamma \text{'}\mathrm{s}$ is observed. This excess is compared with that predicted by quantum chromodynamics for the decay of the $\psi$ into a $\gamma$ and two gluons.