# Pion and Kaon form factors in the perturbative QCD approach

## TL;DR

This paper provides a highly precise perturbative QCD calculation of pion and kaon electromagnetic form factors, including higher-twist corrections and next-to-leading-order effects, confirming theoretical predictions and estimating SU(3) symmetry breaking.

## Contribution

It introduces an advanced calculation incorporating twist-4 power corrections, NLO QCD effects, and both lowest and high Fock states to ensure gauge invariance in meson form factors.

## Key findings

- Confirmed the power-law behavior of twist expansion.
- Demonstrated chiral enhancement at subleading power.
- Estimated SU(3) asymmetry below 30%.

## Abstract

We present the most accurate calculation for the pion and kaon electromagnetic form factors in the framework of perturbative QCD, where the power corrections up to twist-4 of the meson distribution amplitudes and the next-to-leading-order QCD corrections up to subleading power are included. In order to guarantee the gauge invariance of the meson to vacuum matrix element, we take into account both assignments with the lowest Fock state and the high Fock state with an additional valence gluon. Our results confirm the power behaviour of the twist expansion and show the chiral enhancement effect at subleading power in the PQCD approach. We also estimate the $\mathrm{SU(3)}$ asymmetry for the kaon and pion form factors and find that it is smaller than $30 \%$.