UC Irvine

Using 203 pb-1 of data collected by the Mark II detector at the SLAC storage ring PEP, we have measured the radiative width of the η′ for quasireal photons. The width is separately measured in the three reactions e+e-→e+e-η0π+π-, η0→γγ; e+e-→e+e-η0π+π-; η0→π+π-(π0,γ), and e+e-→e+e-ρ0γ, giving a statistically weighted average two-photon width of Γη′→γγ=4.57±0.25±0.44 keV. As a byproduct of the study of the decay mode η′→ργ, we also measured the two-photon decay width of the a2(1320) as Γa2(1320)→γγ=1.03±0.13±0.21 keV.