Isospin-breaking two-nucleon force with explicit Delta-excitations
  We study the leading isospin-breaking contributions to the two-nucleon two-pion exchange potential due to explicit Delta degrees of freedom in chiral effective field theory. In particular, we find important contributions due to the delta mass splittings to the charge symmetry breaking potential that act opposite to the effects induced by the nucleon mass splitting. 
E. Epelbaum, H. Krebs, and Ulf-G. Mei{\ss}ner