Pion-photon transition form factor. Living on the QCD frontier

Abstract

An analysis of all available data (CELLO, CLEO, \babar) in the range $[1÷40]$ GeV${}^2$ for the pion-photon transition form factor in terms of light-cone sum rules with next-to-leading-order accuracy is discussed, including twist-four contributions and next-to-next-to-leading order and twist-six corrections---the latter two via uncertainties. The antithetic trend between the \babar data for the ${\gamma }^{\ast }\gamma {\pi }^0$ and those for the ${\gamma }^{\ast }\gamma \eta ({\eta }^{\prime })$ transition is pointed out, emphasizing the underlying antagonistic mechanisms: endpoint enhancement for the first and endpoint-suppression for the second---each associated with pseudoscalar meson distribution amplitudes with distinct endpoint characteristics.

Comments: 6 pages, 3 figures; needs style files svglov2.clo, svjour2.cls (supplied). Presented at LIGHTCONE 2011, 23 - 27 May, 2011, Dallas, USA. Accepted for publication in Few-Body Systems. In v2 name of second author in [28] corrected. V3 is final version, published online 23. Sep 2011