Pion-pion interaction at low energy
arXiv:hep-ph/9808209
Abstract
A brief discussion of the elastic pion-pion scattering amplitude to two loops in chiral perturbation theory is given. Some technical details of the evaluation of two-loop diagrams are addressed, and results relevant for the pionium decay are presented.
8 pages, 2 figures, Proc. Int. Workshop Hadronic Atoms and Positronium in the Standard Model, Dubna, Russia, May 26-31, 1998