Improved estimates of the pion-photon transition form factor in the $(\mathbf{1\leq Q^2\leq5})$~GeV$^\mathbf{2}$ range and their theoretical uncertainties

TL;DR

This paper provides refined theoretical predictions for the pion-photon transition form factor in the 1-5 GeV^2 range, incorporating higher-order QCD corrections and systematic uncertainties to aid comparison with upcoming experimental data.

Contribution

It advances the theoretical modeling of the pion-photon transition form factor by including NNLO corrections and comprehensive uncertainty estimates within the light-cone sum rules framework.

Findings

Predictions include NNLO QCD corrections and twist-six contributions.

Systematic uncertainties are quantified, highlighting dominant sources.

Results facilitate comparison with future high-precision measurements.

Abstract

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.