Radiative Decays ofηandη′as Probes of Quark Charges

Abstract

Radiative decays of $\ensuremath{\eta}$ and ${\ensuremath{\eta}}^{\ensuremath{'}}$ allow us to test the color hypothesis and to distinguish between fractional- and integral-charge quark models. Accurate measurements of ${\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ and ${\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\gamma}$ are essential to test the analysis and the preliminary conclusion, which favors the three-color model with fractional charges.