Cross-sections for low-energy πgamma; Reactions

We review the cross-sections for low-energy πγ reactions in the framework of chiral perturbation theory. Charged-pion Compton scattering, πγ → πγ , is considered up to one-loop order where the pion's internal structure enters through the difference of the electric and magnetic pion polarizability, α - β . The ongoing COMPASS experiment aims at measuring this important structure constant with high statistics using the Primakoff effect. In the same way, the reaction πγ → ππ serves as a test of the QCD chiral anomaly (via the γ3π -coupling constant F . Furthermore, we calculate the total cross-sections for neutral and charged pion-pair production, πγ → π ππ and πγ → πππ , which are governed by the chiral ππ -interaction. Finally, we investigate the radiative (correction) process πγ → πγγ and calculate the corresponding two-photon mass spectrum. This information will be useful for analyzing the π Primakoff scattering events with photons in the final state. © 2008 Società Italiana di Fisica and Springer-Verlag.