Pion-Photon Transition Form Factor Living on the QCD Frontier

An analysis of all available data (CELLO, CLEO, B A B AR) in the range [1A center dot 40] GeV2 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 B A B AR data for the gamma*gamma pi (0) and those for the gamma*gamma eta(eta') 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.