The Relevance of Contact Terms Versus Pion-Exchange Contributions in the Chiral Effective Field Theory Description of Nucleon-Nucleon Scattering

Abstract

The standard way to demonstrate the relevance of chiral symmetry for the NN interaction is to consider higher partial waves of NN scattering which are ruled entirely by chiral symmetry alone (since contacts vanish). However, in applications of NN-potentials to nuclear structure and reactions, the lower partial waves are the important ones, generating the largest contributions. These lower partial waves are ruled by the dynamics at short range, and so, when the short-range contacts were to dominate over the chiral pion contributions in lower partial waves, then the predictions from "chiral potentials" would have little to do with chiral symmetry. In this thesis, we address this issue and investigate systematically the role of the (chiral) one- and two-pion exchanges, on the one hand, and the effect of the contacts, on the other hand, in the lower partial waves of NN scattering. Our study has also a pedagogical spin-off as it demonstrates in detail how the reproduction of the lower partial-wave phase shifts comes about from the various ingredients of the theory.