Power corrections to the process $γγ^*\to ππ$ 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 $γ^*γ\to ππ$. 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 $2 π$ 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.