Updated determination of the pion-photon transition form factor

In this paper, we study the properties of the pion-photon transition form factor (TFF), γγ*→π⁰, by using the principle of maximum commonality (PMC) to deal with its perturbative QCD contribution up to next-to-next-to-leading order QCD corrections. Applying the PMC, we achieve precise pQCD prediction for the TFF in a large Q²-region without conventional renormalization scale ambiguity. We also discuss the power suppressed nonvalence quark contribution to the TFF, which is important for a sound prediction in a low and intermediate Q²-region, e.g. the nonvalence quark components affect the TFF by about 1% to 23% when Q² changes down from 40 GeV² to 4 GeV². The resultant pion-photon TFF shows a better agreement with previous Belle data. It is hoped that previous discrepancies between the experimental measurements and theoretical predictions could be clarified by the forthcoming precise data on the Belle II measurements.