Production of Photons Associated with theψby 217-GeV/cπ−Mesons

Abstract

Dimuon production is studied in 217-GeV/c ${\pi }^{-}$-hydrogen and ${\pi }^{-}$-beryllium collisions with a lead-glass array to detect photons associated with the $\psi$. The $\psi -\gamma$ mass spectrum shows a 2.6-standard-deviation excess of events above background at ∼3.5 GeV. This excess, if attributed to the decay $\chi (\sim 3.5)\to \psi \gamma$, implies that 0.70±0.28 of the $\psi$'s are produced via radiative decay of one of the $\chi$ states.