Electromagnetic Corrections in Partially Quenched Chiral Perturbation   Theory
  We introduce photons in Partially Quenched Chiral Perturbation Theory and calculate the resulting electromagnetic loop-corrections at NLO for the charged meson masses and decay constants. We also present a numerical analysis to indicate the size of the different corrections. We show that several phenomenologically relevant quantities can be calculated consistently with photons which couple only to the valence quarks, allowing the use of gluon configurations produced without dynamical photons. 
Johan Bijnens and Niclas Danielsson (Lund)