Speaker
Prof.
Vladimir Braun
(University of Regensburg)
Description
We use conformal symmetry to calculate the NNLO anomalous dimension matrix (three loops) for flavor-singlet axial-vector QCD operators for spin N ≤ 8 from a set of gauge-invariant two-point correlation functions. Combining this result with the recent calculation of the two-loop coefficient functions, we carry out the calculation of the $\gamma^* \to \eta\gamma$ and $\gamma^*\to \eta'\gamma$ form factors at large timelike momentum transfers to the NNLO accuracy in perturbative QCD.