Eur. Phys. J. A (2008) 36: 181-188
https://doi.org/10.1140/epja/i2008-10582-9

Regular Article - Theoretical Physics

Cross-sections for low-energy πgamma; reactions

Physik-Department, Technische Universität München, D-85747, Garching, Germany

^* e-mail: nkaiser@physik.tu-muenchen.de

Received: 6 March 2008
Accepted: 24 April 2008
Published online: 15 May 2008

Abstract

We review the cross-sections for low-energy π^-γ reactions in the framework of chiral perturbation theory. Charged-pion Compton scattering, π^-γ → π^-γ , 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_π - β_π . The ongoing COMPASS experiment aims at measuring this important structure constant with high statistics using the Primakoff effect. In the same way, the reaction π^-γ → π^-π⁰ serves as a test of the QCD chiral anomaly (via the γ3π -coupling constant F _γ3π . Furthermore, we calculate the total cross-sections for neutral and charged pion-pair production, π^-γ → π^-π⁰π⁰ and π^-γ → π^-π⁺π^- , which are governed by the chiral ππ -interaction. Finally, we investigate the radiative (correction) process π^-γ → π^-γγ 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.