Comparing antithetic trends of data for the pion-photon transition form factor

TL;DR

This paper compares recent Belle data with earlier BaBar, CLEO, and CELLO results on the pion-photon transition form factor, analyzing implications for the pion's internal structure and arguing that Belle data are more reliable.

Contribution

It provides a comparative theoretical analysis of multiple datasets on the pion-photon transition form factor and discusses their implications for the pion's distribution amplitude.

Findings

Belle data are more consistent and reliable.

Existing data show bifurcation with antithetic trends, which the paper argues is artificial.

Theoretical predictions are classified into three categories.

Abstract

We perform a comparative theoretical study of the data at spacelike momentum transfer for the $\gamma^*\gamma\to\pi^0$ transition form factor, just reported by the Belle Collaboration, vs. those published before by BaBar, also including the older CLEO and CELLO data. Various implications for the structure of the $\pi^0$ distribution amplitude vis-\`a-vis those data are discussed and the existing theoretical predictions are classified into three distinct categories. We argue that the actual bifurcation of the data with antithetic trends is artificial and reason that the Belle data are the better option.