Photon transitions in ψ(2S) decays to χcJ(1P) and ηc(1S)

Abstract

We have studied the inclusive photon spectrum in $\ensuremath{\psi}(2S)$ decays using the CLEO III detector. We present the most precise measurements of electric dipole (E1) photon transition rates for $\ensuremath{\psi}(2S)\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\chi}}_{cJ}(1P)$ ($J=0,1,2$). We also confirm the hindered magnetic dipole (M1) transition, $\ensuremath{\psi}(2S)\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\eta}}_{c}(1S)$. However, the direct M1 transition $\ensuremath{\psi}(2S)\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\eta}}_{c}(2S)$ observed by the Crystal Ball as a narrow peak at a photon energy of 91 MeV is not found in our data.