Two-pion exchange electromagnetic current in chiral effective field theory using the method of unitary transformation

Abstract

Using the method of unitary transformation in combination with chiral effective field theory we derive the two-pion exchange contributions to the two-nucleon electromagnetic current. A formal definition of the current operator in this scheme and the power counting is presented. We discuss the implications of additional unitary transformations that have to be present to ensure the renormalizability of the one-pion exchange current. Further, we give explicit and compact results for the current in coordinate-space.