γ γ → η , η ′ transition form factors

Using a continuum approach to the hadron bound-state problem, we calculate γ∗γ → η,η′ transition form factors on the entire domain of spacelike momenta, for comparison with existing experiments and in anticipation of new precision data from next-generation e+e− colliders. One novel feature is a model for the contribution to the Bethe-Salpeter kernel deriving from the non-Abelian anomaly, an element which is crucial for any computation of η,η′ properties. The study also delivers predictions for the amplitudes that describe the light- and strange-quark distributions within the η,η′. Our results compare favorably with available data. Important to this at large Q2 is a sound understanding of QCD evolution, which has a visible impact on the η′ in particular. Our analysis also provides some insights into the properties of η,η′ mesons and associated observable manifestations of the non-Abelian anomaly.