Photon-pion transition form factor at high photon virtualities within the nonlocal chiral quark model

Recently, the BABAR collaboration reported the measurements of the photon-pion transition form factor F (pi gamma gamma*)(Q (2)), 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 exist two asymptotic regimes for the pion transition form factor. One regime with the asymptotic behavior F (pi gamma*gamma)(Q (2)) similar to 1/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*gamma)(Q (2)) similar to ln(Q (2))/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.