We examine two-body radiative decays of quarkonium states Ô→γ+ζ in order to study the effects of the spin of the ζ on decay widths; ζ stands for any elementary particle or resonance. Using effective ζ couplings in a calculation which goes beyond the Wilczek approximation, we find that in all cases examined, $J_{\zeta }$${=0\mathrm{}}^{\pm }$, $1^{+}$, $2^{\pm }$, spin has little effect on the ratio Γ(Ô(2S)→γ+ζ)/ Γ(Ô(1S)→γ+ζ) except for ζ masses close to the phase-space limit.

• Received 10 March 1986

DOI:https://doi.org/10.1103/PhysRevD.34.1418