# Towards high-order calculations of three-nucleon scattering in chiral effective field theory

## TL;DR

This paper reviews the progress in high-order chiral effective field theory calculations for three-nucleon scattering, demonstrating good agreement with data up to third order and discussing future challenges for fifth order accuracy.

## Contribution

It provides selected results for nucleon-deuteron scattering using regularized chiral potentials and explores the impact of higher-order three-nucleon forces on observables.

## Key findings

- Good description of experimental data at third chiral order
- Higher-order effects are significant for polarization observables
- Pushing to fifth order is necessary for high-precision modeling

## Abstract

We discuss the current status of chiral effective field theory in the three-nucleon sector and present selected results for nucleon-deuteron scattering observables based on semilocal momentum-space-regularized chiral two-nucleon potentials together with consistently regularized three-nucleon forces up to third chiral order. Using a Bayesian model for estimating truncation errors, the obtained results are found to provide a good description of the experimental data. We confirm our earlier findings that a high-precision description of nucleon-deuteron scattering data below pion production threshold will require the theory to be pushed to fifth chiral order. This conclusion is substantiated by an exploratory study of selected short-range contributions to the three-nucleon force at that order, which, as expected, are found to have significant effects on polarization observables at intermediate and high energies. We also outline the challenges that will need to be addressed in order to push the chiral expansion of three-nucleon scattering observables to higher orders.