Two-nucleon scattering in a modified Weinberg approach with a symmetry-preserving regularization

We consider the nucleon-nucleon scattering problem by applying time-ordered perturbation theory to the Lorentz-invariant formulation of baryon chiral perturbation theory. We employ a higher-derivative symmetry-preserving regularization to obtain an integral equation for the scattering amplitude, which permits a non-perturbative treatment of subleading contributions to the nucleon-nucleon potential. The resulting formulation is used to quantify finite regulator artefacts in two-nucleon phase shifts as well as in the chiral extrapolations of the S-wave scattering lengths and the deuteron binding energy. Our approach can be straightforwardly extended to analyse few-nucleon systems and processes involving external electroweak sources.