Abstract
We reconsider QCD factorization for the leading power contribution to the γ*γ → π0 form factor Fγ*γ→π0(Q2) at one loop using the evanescent operator approach, and demonstrate the equivalence of the resulting factorization formulae derived with distinct prescriptions of γ5 in dimensional regularization. Applying the light-cone QCD sum rules (LCSRs) with photon distribution amplitudes (DAs) we further compute the subleading power contribution to the pion-photon form factor induced by the “hadronic” component of the real photon at the next-to-leading-order in \( \mathcal{O}\left({\alpha}_s\right) \), with both naive dimensional regularization and ’t Hooft-Veltman schemes of γ5. Confronting our theoretical predictions of Fγ*γ→π0 (Q2) with the experimental measurements from the BaBar and the Belle Collaborations implies that a reasonable agreement can be achieved without introducing an “exotic” end-point behaviour for the twist-2 pion DA.
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Wang, YM., Shen, YL. Subleading power corrections to the pion-photon transition form factor in QCD. J. High Energ. Phys. 2017, 37 (2017). https://doi.org/10.1007/JHEP12(2017)037
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DOI: https://doi.org/10.1007/JHEP12(2017)037