Power corrections to the process $\gamma\gamma^*\to \pi\pi$ in the Light-Cone Sum Rules approach

Abstract

We applied QCD Light Cone Sum Rules to estimate power corrections to the helicity-conserving amplitude in the process $\gamma^*\gamma\to \pi\pi$. We found that above $Q^2 \sim 4$ GeV$^2$ power corrections are numerically small and the twist-2 part dominates.The amplitude can be reliably calculated in this region using models of $2 \pi$ distribution amplitudes as an input. We found that the magnitude of the NLO corrections depends rather strongly on the normalization of the gluonic distribution amplitude.