Direct photon production at theψ

Abstract

We present results of a detailed analysis of inclusive direct photon production at the $\psi \mathrm{}\left(3095\right)\mathrm{}$. The direct-photon momentum distribution for $x>\mathrm{}0.4\mathrm{}$ is presented and compared with the leading-order quantum-chromodynamic prediction. The total production rate is found to be consistent with theoretical expectations, but the observed momentum distribution is considerably softer. Results of an analysis of some inclusive properties of the hadronic system recoiling against the direct photon are presented. The mean charged-particle and $K_s$ multiplicities are presented as functions of the invariant mass of the hadronic system. These data agree well with the corresponding mean multiplicities measured in $e^{+}{e}^{-}$ annihilations at center-of-mass energies comparable to the invariant mass of the hadronic system.