# What can be learned from the transition form factor $\gamma^*\gamma^*\to\eta'$: feasibility study

## TL;DR

This paper analyzes BaBar's recent measurements of the $ ext{η'}$ transition form factor from two virtual photons, testing QCD factorization and exploring sensitivity to power corrections and decay constants.

## Contribution

It provides the first test of the collinear factorization approach for $ ext{η'}$ production and assesses the data's agreement with perturbative QCD.

## Key findings

- Data agrees with perturbative QCD predictions.
- The measurement is sensitive to power corrections and decay constants.
- Identifies kinematic regions for probing interesting physics.

## Abstract

We present an analysis of the recent measurement of $\eta'$-meson production by two virtual photons made by BaBar collaboration. It is the first measurement of a transition form factor which is entirely within the kinematic regime of the collinear factorization approach and thus provides a clean test of QCD factorization theorem for distribution amplitudes (DAs). We demonstrate that the data is in agreement with the perturbative QCD. Also, we show that it is sensitive to power corrections to the factorization theorem and to the decay constants. We discuss features of the meson production cross-section and point out the kinematic regions that are sensitive to interesting physics. We also provide an estimation of uncertainties on the extraction of DA parameters.