The relation for transition form factors of $\eta$ and ${\eta }^{\prime }$ 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.

• Received 19 July 2011

DOI:https://doi.org/10.1103/PhysRevD.84.051901