Radiation pions in two-nucleon effective field theory

For interactions involving two or more nucleons it is useful to divide pions into three classes: potential radiation, and soft. The momentum threshold for the production of radiation pions is Q(r) = root M(N)m(pi). We show that radiation pions can be included systematically with a power counting in Q(r). The leading order radiation pion graphs which contribute to NN scattering are evaluated in the PDS and OS renormalization schemes and are found to give a small contribution. The power counting for soft pion contributions is also discussed. (C) 2000 Elsevier Science B.V. All rights reserved.