Systematic estimation of theoretical uncertainties in the calculation of the pion-photon transition form factor using light-cone sum rules

We consider the calculation of the pion-photon transition form factor F super([gamma]*[gamma][pi]0)(Q super(2)) within light-cone sum rules focusing attention to the low-mid region of momenta. The central aim is to estimate the theoretical uncertainties which originate from a wide variety of sources related to (i) the relevance of next-to-next-to-leading order radiative corrections (ii) the influence of the twist-four and the twist-six term (iii) the sensitivity of the results on auxiliary parameters, like the Borel scale M super(2), (iv) the role of the phenomenological description of resonances, and (v) the significance of a small but finite virtuality of the quasireal photon. Predictions for F super([gamma]*[gamma][pi]0)(Q super(2)) are presented which include all these uncertainties and found to comply within the margin of experimental error with the existing data in the Q super(2) range between 1 and 5GeV super(2), thus justifying the reliability of the applied calculational scheme. This provides a solid basis for confronting theoretical predictions with forthcoming data bearing small statistical errors.