Chiral anomaly, triangle loop and the the $\gamma {\gamma }^{\ast }\to {\pi }^0$ form factor

T. N. Pham, X. Y. Pham

The recent BaBar measurements of the $\gamma {\gamma }^{\ast }\to {\pi }^0$ form factor show spectacular deviation from perturbative QCD computations for large space-like $Q^2$. At $34\mathrm{Ge}{\mathrm{V}}^2$…