Improved estimates of the pion-photon transition form factor in the (1 ≤ Q2 ≤ 5) GeV2 range and their theoretical uncertainties
1 Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna, Russia
2 Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, P. R. China
3 Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum, Germany
Published online: 22 March 2017
We consider the pion-photon transition form factor at low to intermediate spacelike momenta within the theoretical framework of light-cone sum rules. We derive predictions which take into account all currently known contributions stemming from QCD perturbation theory up to the next-to-next-to-leading order (NNLO) and by including all twist terms up to order six. In order to enable a more detailed comparison with forthcoming high-precision data, we also estimate the main systematic theoretical uncertainties, stemming from various sources, and discuss their influence on the calculations — in particular the dominant one related to the still uncalculated part of the NNLO contribution. The analysis addresses, in broad terms, also the role of the twist-two pion distribution amplitude derived with different approaches.
© The Authors, published by EDP Sciences, 2017
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