2-Nucleon 1-Loop Corrections to Pion Double Charge Exchange within Heavy   Baryon Chiral Perturbation Theory
  One-loop corrections at the two-nucleon level to Pion Double Charge exchange (DCX) scattering off a nuclear target at threshold, are calculated within the framework of Heavy Baryon Chiral Perturbation Theory (HBChPT). An estimate for the (2-nucleon) 1-loop correction is obtained in the static limit and using an impulse approximation. We find a small (1.6%) increase relative to the leading order tree graphs. 
A. Misra (1), D. S. Koltun (2) ((1) Indian Institute of Technology,   Kanpur, India, (2) University of Rochester, USA)