Axial anomaly and mixing: from real to highly virtual photons

TL;DR

This paper derives a universal relation for eta and eta' meson transition form factors across all photon virtualities using nonperturbative QCD sum rules and axial anomaly, aligning well with experimental data.

Contribution

It introduces a new, exact relation for meson transition form factors valid at all virtual photon momenta, based on nonperturbative QCD and axial anomaly.

Findings

Relation agrees with experimental data

Valid for all virtual photon momenta

Expresses form factors via meson decay constants

Abstract

The relation for transition form factors of eta and eta' mesons is obtained by combining the exact nonperturbative QCD sum rule, following from the dispersive representation of axial anomaly, and quark-hadron duality. It is valid at all virtual photon momenta and allows one to express the transition form factors entirely in terms of meson decay constants. This relation is in a good agreement with experimental data.