Pion-photon transition form factor in light-cone sum rules

TL;DR

This paper investigates the pion-photon transition form factor using light-cone sum rules, revealing discrepancies among experimental data sets and providing predictions based on a longstanding pion distribution amplitude model.

Contribution

It offers a detailed analysis of pion distribution amplitudes constrained by experimental data, highlighting discrepancies and providing predictions consistent with some datasets.

Findings

Discrepancy of 2.7-3 sigma between data sets from CELLO, CLEO, Belle, and BaBar.

Predictions align with Belle data but not with BaBar data beyond 9 GeV^2.

Constraints on pion distribution amplitude from experimental data.

Abstract

We extract constraints on the pion distribution amplitude from available data on the pion-photon transition form factor in the framework of light-cone sum rules. A pronounced discrepancy $(2.7-3)\sigma$ between the Gegenbauer expansion coefficients extracted from the CELLO, CLEO, and Belle experimental data relative to those from BaBar is found. Predictions for the pion-photon transition form factor are presented by employing a pion distribution amplitude obtained long ago from QCD sum rules with nonlocal condensates. These predictions comply with the Belle data but disagree with those of BaBar beyond 9 GeV$^2$.