Subleading power corrections to the pion-photon transition form factor in QCD

Abstract

We reconsider QCD factorization for the leading power contribution to the ${\gamma }^{\ast }\gamma \to {\pi }^0$ form factor $F_{{\gamma }^{\ast }\gamma \to {\pi }^0}(Q^2)$ at one loop using the evanescent operator approach, and demonstrate the equivalence of the resulting factorization formulae derived with distinct prescriptions of ${\gamma }_5$ 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 $\mathcal{O}({\alpha }_s)$, with both naive dimensional regularization and 't Hooft-Veltman schemes of ${\gamma }_5$. Confronting our theoretical predictions of $F_{{\gamma }^{\ast }\gamma \to {\pi }^0}(Q^2)$ 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.

36 pages, 8 figures

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• The $D^{\ast }D\pi$ and $B^{\ast }B\pi$ couplings from light-cone sum rules
• Pion-photon transition form factor in LCSR and tests of asymptotics
• QCD factorization for the four-body leptonic $B$-meson decays
• Precision calculations of the double radiative bottom-meson decays in soft-collinear effective theory
• Global Analysis of hadronic two-body B decays in the perturbative QCD approach
• A Procedure g5anchor to Anchor ${\gamma }_5$ in Feynman Diagrams for the Standard Model
• The PQCD approach towards to next-to-leading order: a short review
• Factorization of radiative leptonic D-meson decay with sub-leading power corrections
• Power corrections to the pion transition form factor from higher-twist distribution amplitudes of photon
• Constraint of $\xi$-moments calculated with QCD sum rules on the pion distribution amplitude models
• An improved calculation of the $D_{(s)}^{\ast }{D}_{(s)}V$ and $B_{(s)}^{\ast }{B}_{(s)}V$ couplings from light-cone sum rules
• Strange quark mass effect in $B_s\to \gamma \gamma ,\gamma \ell \bar{\ell }$ decays
• QCD calculations of radiative heavy meson decays with subleading power corrections