Two-Pion Exchange Contributions to the Nucleon-Nucleon Interaction from the Roper Resonance

TL;DR

This paper investigates the impact of the Roper resonance on the long-range two-pion-exchange potential in nucleon-nucleon interactions, showing it notably improves phase shift descriptions, especially for D waves.

Contribution

It introduces the Roper resonance into the chiral perturbation theory framework for NN interactions, providing a novel analysis of its effects on phase shifts and resonance saturation.

Findings

Roper resonance significantly affects D-wave phase shifts.

Inclusion of the Roper improves the overall phase shift description.

The Roper contribution is sizeable and relevant for NN interaction models.

Abstract

We derive the long-range components of the nucleon-nucleon (NN) two-pion-exchange potential with an intermediate Roper resonance. Leading-order interactions in heavy-baryon chiral perturbation theory are considered. NN phase shifts with orbital angular momentum $L\geq 2$ are calculated in first-order perturbation theory and compared to those obtained without the Roper resonance. We show that the Roper contribution is sizeable for $D$ waves and improves the description of phase shifts for all the partial waves slightly. We also discuss the role of the Roper resonance in the NN interaction in the framework of resonance saturation.