Rigorous constraints on three-nucleon forces in chiral effective field theory from fast and accurate calculations of few-body observables

Artikel i vetenskaplig tidskrift, 2021

We explore the constraints on the three-nucleon force (3NF) of chiral effective field theory (χEFT) that are provided by bound-state observables in the A=3 and A=4 sectors. Our statistically rigorous analysis incorporates experimental error, computational method uncertainty, and the uncertainty due to truncation of the χEFT expansion at next-to-next-to-leading order. A consistent solution for the H3 binding energy, the He4 binding energy and radius, and the H3β-decay rate can only be obtained if χEFT truncation errors are included in the analysis. The β-decay rate is the only one of these that yields a nondegenerate constraint on the 3NF low-energy constants, which makes it crucial for the parameter estimation. We use eigenvector continuation for fast and accurate emulation of no-core shell model calculations of the few-nucleon observables. This facilitates sampling of the posterior probability distribution, allowing us to also determine the distributions of the parameters that quantify the truncation error. We find a χEFT expansion parameter of Q=0.33±0.06 for these observables.