An updated determination of the pion-photon transition form factor

Abstract

In this paper, we study the properties of the pion-photon transition form factor (TFF), $γγ^{\ast} \rightarrow π^{0}$, by using the principle of maximum commonality (PMC) to deal with its perturbative QCD contribution up to next-to-next-to-leading order (NNLO) QCD corrections. Applying the PMC, we achieve precise pQCD approximant for the TFF in large $Q^2$-region without conventional renormalization scale ambiguity. We also discuss the power suppressed non-valence quark contribution to the TFF, which is important for a sound prediction in low and intermediate $Q^2$-region, e.g. the non-valence quark components affect the TFF by about $1\%$ to $23\%$ when $Q^2$ changes down from $40\mathrm{Ge}{\mathrm{V}}^2$ to $4\mathrm{Ge}{\mathrm{V}}^2$. 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 forth-coming precise data on the Belle II measurements.

7 pages, 6 figures