Measurement of the Direct Photon Spectrum in ${\rm Y}(1S)$ Decays

CLEO Collaboration, B. Nemati et al

Using data taken with the CLEO II detector at the Cornell Electron Storage Ring, we have determined the ratio of branching fractions: $R_γ \equiv Γ(Υ(1S) \rightarrow γgg)/Γ(Υ(1S) \…