γ * γ → η , η ' transition form factors

Abstract

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 favourably with available data. Important to this at large-Q 2 is a sound understanding of QCD evolution, which has a visible impact on the η' in particular. In conclusion, our analysis also provides some insights into the properties of η, η' mesons and associated observable manifestations of the non-Abelian anomaly.