Charge-dependent nucleon-nucleon potential from chiral effective field theory

We discuss charge-symmetry and charge-independence breaking in a chiral eff ective field theory approach for few-nucleon systems based on a modified We inberg power counting. We construct a two-nucleon potential with bound and scattering states generated by means of a properly regularized Lippmann-Sch winger equation. We systematically introduce strong isospin-violating and e lectromagnetic operators in the theory. We use standard procedures to treat the Coulomb potential between two protons in momentum space. We present re sults for phase shifts in the proton-proton, neutron-proton and the neutron -neutron systems. We discuss the various contributions to charge dependence and charge-symmetry breaking observed in the nucleon-nucleon scattering le ngths. (C) 2001 Elsevier Science B.V. All rights reserved.