The eta (eta') gamma transition form factor and the gluon-gluon distribution amplitude

TL;DR

This paper analyzes eta and eta' transition form factors using perturbative QCD to extract distribution amplitude coefficients and predict the gluon-gluon-eta' vertex, incorporating experimental data and mixing schemes.

Contribution

It provides a comprehensive NLO analysis of eta and eta' transition form factors, extracting distribution amplitudes and predicting the g*g*eta' vertex function.

Findings

Extracted Gegenbauer coefficients for quark and gluon components.

Predicted the g*g*eta' vertex function.

Commented on recent BELLE results for pi-gamma form factor.

Abstract

The eta-gamma and eta'-gamma transition form factors are analyzed to leading-twist accuracy and next-to-leading order (NLO) of perturbative QCD. Using an eta-eta' mixing scheme and all currently available experimental data the lowest Gegenbauer coefficients of the distribution amplitudes for the valence octet and singlet quark-antiquark and the gluon-gluon Fock components are extracted. Predictions for the g*g*eta' vertex function are presented. We also comment on the new BELLE results for the pi-gamma transition form factor.