Chiral Three-Nucleon Interactions in Light Nuclei, Neutron-$\alpha$ Scattering, and Neutron Matter

TL;DR

This paper uses quantum Monte Carlo methods with chiral effective field theory interactions to accurately model light nuclei, neutron-$eta$ scattering, and neutron matter, fitting low-energy couplings to experimental data.

Contribution

It introduces a novel fitting of low-energy couplings to spin-orbit splitting in neutron-$eta$ scattering, improving the predictive power of chiral interactions for nuclear systems.

Findings

Chiral interactions at N$^2$LO reproduce properties of light nuclei and neutron matter.

Fitting to spin-orbit splitting improves phase shift predictions.

Chiral interactions outperform phenomenological models in these systems.

Abstract

We present quantum Monte Carlo calculations of light nuclei, neutron-$\alpha$ scattering, and neutron matter using local two- and three-nucleon ($3N$) interactions derived from chiral effective field theory up to next-to-next-to-leading order (N$^2$LO). The two undetermined $3N$ low-energy couplings are fit to the $^4$He binding energy and, for the first time, to the spin-orbit splitting in the neutron-$\alpha$ $P$-wave phase shifts. Furthermore, we investigate different choices of local $3N$-operator structures and find that chiral interactions at N$^2$LO are able to simultaneously reproduce the properties of $A=3,4,5$ systems and of neutron matter, in contrast to commonly used phenomenological $3N$ interactions.