# Power Corrections to Pion Transition Form Factor in Perturbative QCD Approach

## TL;DR

This paper calculates power corrections to the pion transition form factor using perturbative QCD with $k_T$ factorization, finding that these corrections are small due to cancellations, supporting the form factor's use in constraining pion wave functions.

## Contribution

It provides a detailed analysis of power corrections from higher twist pion wave functions and photon structure, showing their negligible impact due to cancellations within the perturbative QCD framework.

## Key findings

- Power corrections are strongly canceled, resulting in minimal overall impact.
- Leading power predictions remain stable with joint resummation.
- Results can explain BaBar and Belle data depending on pion wave function parameters.

## Abstract

In this paper we calculate the power corrections to the pion transition form factor within the framework of perturbative QCD approach on the basis of $k_T$ factorization. The power suppressed contributions from higher twist pion wave functions and the hadronic structure of photon are investigated. We find that there exists strong cancellation between the two kinds contributions, thus the total power corrections considered currently are very small, and the prediction of the leading power contribution with joint resummation improved perturbative QCD approach is almost unchanged. This result confirms that the pion transition form factor is a good platform to constrain the nonperturbative parameters in pion wave functions. Moreover, our result can accommodate the anomalous data from BaBar, or agrees with results from Belle according to the choice of Gegebauer moment in the pion wave function, and the more precise experimental data from Belle-II is expected.