Eiras, DolorsSoto Riera, Joan2010-05-062010-05-0620000556-2821https://hdl.handle.net/2445/12439The various dynamical scales below the pion mass involved in $\pi^{+}$ $\pi^{-}$ atoms are sequentially integrated out using non-relativistic effective field theory techniques. This allows us to systematically organise the corrections to the energy levels and decay width. We present our results in terms of a single unknown constant which may be obtained by matching to the Chiral Lagrangian with electromagnetic interactions at two loops.11 p.application/pdfeng(c) The American Physical Society, 2000Teoria de camps (Física)Partícules (Física nuclear)Interaccions electromagnètiquesMesons (Física nuclear)Field theory (Physics)Particles (Nuclear physics)Electroweak interactionsMesonsinfo:eu-repo/semantics/article170163info:eu-repo/semantics/openAccess