Transition form factors $\gamma^*\gamma\to\eta$ and $\gamma^*\gamma\to\eta'$ in QCD

TL;DR

This paper refines the QCD theoretical calculations of transition form factors for gamma-gamma to eta and eta' processes by including higher-order corrections, charm quark effects, and flavor symmetry breaking, and compares with experimental data.

Contribution

It provides an updated, comprehensive QCD framework for calculating these form factors, incorporating next-to-leading order corrections and additional effects previously neglected.

Findings

Improved agreement with experimental data.

Quantitative estimates of charm quark contributions.

Assessment of SU(3)-flavor breaking effects.

Abstract

We update the theoretical framework for the QCD calculation of transition form factors $\gamma^*\gamma\to\eta$ and $\gamma^*\gamma\to\eta'$ at large photon virtualities including full next-to-leading order analysis of perturbative corrections, the charm quark contribution, and taking into account SU(3)-flavor breaking effects and the axial anomaly contributions to the power-suppressed twist-four distribution amplitudes. The numerical analysis of the existing experimental data is performed with these improvements.