Nucleon-nucleon scattering from effective field theory

We perform a non-perturbative calculation of the 1S0 NN scattering amplitude, using an effective field theory (EFT) expansion. The expansion we advocate is a modification of what has been used previously; it is not a chiral expansion in powers of mπ. We use dimensional regularization throughout, and the MS renormalization scheme; our final result depends only on physical observables. We show that the EFT expansion of the quantity |p| cotθ(p) converges at momenta much greater than the scale A that characterizes the derivative expansion of the EFT Lagrangian. Our conclusions are optimistic about the applicability of an EFT approach to the quantitative study of nuclear matter.