Pion-photon transition form factor in light-cone sum rules

Abstract

We extract constraints on the pion distribution amplitude from available data on the pion-photon transition form factor in the framework of light-cone sum rules. A pronounced discrepancy $(2.7-3)\sigma$ between the Gegenbauer expansion coefficients extracted from the CELLO, CLEO, and Belle experimental data relative to those from BaBar is found. Predictions for the pion-photon transition form factor are presented by employing a pion distribution amplitude obtained long ago from QCD sum rules with nonlocal condensates. These predictions comply with the Belle data but disagree with those of BaBar beyond 9 GeV${}^2$.

Comments: 5 pages, 3 figures, talk presented by the first author at the QCD@Work Conference, Lecce (Italy), 18 - 21 June, 2012. v2 minor typos corrected