The axial-vector contributions in two-photon reactions: pion transition form factor and deeply-virtual Compton scattering at NNLO in QCD

Abstract

Using the approach based on conformal symmetry we calculate the two-loop coefficient function for the axial-vector contributions to two-photon processes in the $\overline{\mathrm{MS}}$ scheme. This is the last missing element for the complete next-to-next-to-leading order (NNLO) calculation of the the pion transition form factor ${\gamma }^{\ast }\gamma \to \pi$ in perturbative QCD. The corresponding high-statistics measurement is planned by the Belle II collaboration and will allow one to put strong constraints on the pion light-cone distribution amplitude. The calculated NNLO corrections prove to be rather large and have to be taken into account. The same coefficient function determines the contribution of the axial-vector generalized parton distributions to deeply-virtual Compton scattering which is investigated at the JLAB 12 GeV accelerator, by COMPASS at CERN, and in the future will be studied at the Electron Ion Collider EIC.

Published version. Two misprints corrected in the ancillary file

References in corpus (4)

• Algorithms for the symbolic integration of hyperlogarithms with applications to Feynman integrals
• Measurement of gamma gamma* --> pi0 transition form factor at Belle
• Anomalous dimensions of high-spin operators beyond the leading order
• Towards a fitting procedure for deeply virtual Compton scattering at next-to-leading order and beyond

Cited by in corpus (10)

• Pion and Kaon Distribution Amplitudes from Lattice QCD
• Next-to-Next-to-Leading-Order QCD Prediction for the Photon-Pion Form Factor
• Next-to-leading-power kinematic corrections to DVCS: a scalar target
• QCD Predictions for Meson Electromagnetic Form Factors at High Momenta: Testing Factorization in Exclusive Processes
• Lattice QCD Calculation of $x$-dependent Meson Distribution Amplitudes at Physical Pion Mass with Threshold Logarithm Resummation
• NLO corrections to the deeply virtual meson production revisited: impact on the extraction of generalized parton distributions
• Resummation of threshold logarithms in deeply-virtual Compton scattering
• An updated determination of the pion-photon transition form factor
• Assessing the impact of the electron ion collider in China on Deeply Virtual Compton Scattering
• Conformal moments of the two-loop coefficient functions in DVCS