QCD sum rules and Compton scattering

The authors extend QCD sum rule analysis to moderate energy fixed angle Compton scattering. In this kinematic region there is a strong similarity to the sum rule treatment of electromagnetic form factors, although the four-point amplitude requires a modification of the Borel transform. To illustrate their method, they derive the sum rules for helicity amplitudes in pion Compton scattering and estimate their large-t behavior in the local duality approximation.