Isospin breaking in low-energy charged pion–kaon elastic scattering

We use chiral perturbation theory to evaluate the scattering amplitude for the process at leading and next-to-leading orders in the chiral counting and in the presence of isospin breaking effects. We also discuss the influence of the latter on the combination of the -wave scattering lengths which is relevant for the 2S–2P energy level shift of atoms. Received: 19 November 2001 / Revised version: 21 December 2001 / Published online: 5 April 2002