Isospin-breaking corrections in the pion-deuteron scattering length
  It is shown that isospin-breaking corrections to the pion-deuteron scattering length can be very large, because of the vanishing of the isospin-symmetric contribution to this scattering length at leading order in chiral perturbation theory. We further demonstrate that these corrections can explain the bulk of the discrepancy between the recent experimental data on pionic hydrogen and pionic deuterium. We also give the first determination of the electromagnetic low-energy constant f1. 
Ulf-G. Mei{\ss}ner (University of Bonn and FZ J\"ulich), Udit Raha   (University of Bonn), Akaki Rusetsky (University of Bon...