Light Cone Sum Rules for the pi0-gamma*-gamma Form Factor Revisited

TL;DR

This paper revises theoretical calculations of the pi0-gamma*-gamma form factor using Light Cone Sum Rules, incorporating higher-order corrections and comparing with experimental data, suggesting the pion distribution amplitude may be more complex than previously thought.

Contribution

It updates the LCSR calculations of the pi0-gamma*-gamma form factor with higher polynomial terms and twist-six corrections, providing a more comprehensive theoretical analysis.

Findings

Results align with QCD predictions at large momentum transfers.

Recent BaBar data are consistent with the revised theoretical framework.

Indications that the pion distribution amplitude might have a more intricate structure.

Abstract

We provide a theoretical update of the calculations of the pi0-gamma*-gamma form factor in the LCSR framework, including up to six polynomials in the conformal expansion of the pion distribution amplitude and taking into account twist-six corrections related to the photon emission at large distances. The results are compared with the calculations of the B-> pi l nu decay and pion electromagnetic form factors in the same framework. Our conclusion is that the recent BaBar measurements of the pi0-gamma*-gamma form factor at large momentum transfers are consistent with QCD, although they do suggest that the pion DA may have more structure than usually assumed.