Transition form factors in ${\pi }^0$, $\eta$, and ${\eta }^{\prime }$ couplings to $\gamma {\gamma }^{*}$

Recent measurements of the transition form factors for the $P\gamma {\gamma }^{*}$ vertices, with $P={\pi }^0$, $\eta$, and ${\eta }^{\prime }$, are compared with different models. These include vector-meson dominance, constituent-quark loops, the QCD-inspired interpolation by Brodsky-Lepage, and chiral perturbation theory. General agreement is observed and differences—due to SU(3) breaking—are stressed and discussed.