Ab initio many-body calculations of nucleon-4He scattering with three-nucleon forces

TL;DR

This paper develops an advanced ab initio framework incorporating three-nucleon forces to accurately model nucleon-4He scattering, achieving improved phase shift predictions and better agreement with experimental data.

Contribution

It introduces a formalism to include three-nucleon interactions in ab initio scattering calculations, extending the no-core shell model/resonating-group method.

Findings

Inclusion of 3N forces enhances spin-orbit splitting.

Achieves good agreement with experimental phase shifts.

Improves differential cross section predictions.

Abstract

We extend the ab initio no-core shell model/resonating-group method to include three-nucleon (3N) interactions for the description of nucleon-nucleus collisions. We outline the formalism, give algebraic expressions for the 3N-force integration kernels, and discuss computational aspects of two alternative implementations. The extended theoretical framework is then applied to nucleon-4He scattering using similarity-renormalization-group (SRG) evolved nucleon-nucleon plus three-nucleon potentials derived from chiral effective field theory. We analyze the convergence properties of the calculated phase shifts and explore their dependence upon the SRG evolution parameter. We include up to six excited states of the 4He target and find significant effects from the inclusion of the chiral 3N force, e.g., it enhances the spin-orbit splitting between the 3/2- and 1/2- resonances and leads to an improved agreement with the phase shifts obtained from an accurate R-matrix analysis of the five-nucleon experimental data. We find remarkably good agreement with measured differential cross sections at various energies, while analyzing powers manifest larger deviations from experiment for certain energies and angles.