Electromagnetic Corrections to Charged Pion Scattering at Low Energies
  The electromagnetic corrections to the low energy scattering amplitude involving charged pions only are investigated at leading and next-to-leading orders in the two-flavour chiral expansion. As an application, the corresponding variation in the strong $2S-2P$ level shift is evaluated. The relative variation is of the order of 5%. 
M. Knecht and A. Nehme (CPT, Marseille)