JETP Letters: issues online

Recently, the BABAR collaboration reported the measurments of the photon-pion transition form factor $F_{\pi\gamma\gamma^{\ast}}\left(Q^{2}\right)$ , which are in strong contradiction to the predictions of the standard factorization approach to perturbative QCD. In the present work, based on a nonperturbative approach to the QCD vacuum and on rather universal assumptions, we show that there exists two asymptotic regimes for the pion transition form factor. One regime with asymptotics $F_{\pi\gamma^{\ast}\gamma}\left(Q^{2}\right) \sim1/Q^{2}$ corresponds to the result of the standard QCD factorization approach, while other violates the standard factorization and leads to asymptotic behavior as $F_{\pi\gamma^{\ast}\gamma}\left(Q^{2}\right) \sim\ln\left(Q^{2}\right) /Q^{2}$ . Furthermore, considering specific nonlocal chiral quark models, we find the region of parameters, where the existing CELLO, CLEO and BABAR data for the pion transition form factor are successfully described.