Photon-pion transition form factor: BABAR puzzle is cracked

Understand

Recently, the BABAR collaboration published (arXiv:0905.4778) data for the photon-pion transition form factor $F_{\pi\gamma\gamma^{\ast}}(Q^{2})$, which are in strong contradiction to the predictions of the standard factorization approach to perturbative QCD.

• Immediately afterwards, two mechanisms were suggested (A.E.
• Dorokhov, arXiv:0905.4577; A.V.
• Radyushkin, arXiv:0906.0323), that logarithmically enhance the form factor asymptotics and therefore provide a qualitatively satisfactory description of the BABAR data.