η and η ′ transition form factors from rational approximants

The η and η′ transition form factors in the spacelike region are analyzed at low and intermediate energies in a model-independent way through the use of rational approximants. The slope and curvature parameters of the form factors as well as their values at zero and infinity are extracted from experimental data. The impact of these results on the mixing parameters of the η-η′ system and the pseudoscalar-exchange contributions to the hadronic light-by-light scattering part of the anomalous magnetic moment aμ are also discussed. © 2014 American Physical Society.