Two-loop integrals in chiral perturbation theory
J. Gasser1 - M.E. Sainio2
1 Institute of Theoretical Physics, University of Berne,
Sidlerstrasse 5, CH-3012 Berne, Switzerland
2 Department of Physics, University of Helsinki, P.O. Box 9, FIN-00014 Helsinki, Finland
Received: 14 April 1998 / Published online: 7 August 1998
We consider chiral perturbation theory in the meson sector at order E6. In the terminology of the external field technique, the genuine two-loop diagrams so generated are of the sunset type. We discuss the evaluation of several of these in the case where the masses of the particles running in the loops are equal. In particular, we present integral representations that are suitable for the evaluation of diagrams in kinematical regions where branch points and cuts are present.