Roles of chiral three-nucleon forces in nucleon-nucleus scattering

TL;DR

This paper explores how chiral three-nucleon forces influence nucleon-nucleus elastic scattering, revealing their effects on the potential's attraction and absorption, especially at backward angles, through advanced nuclear interaction models.

Contribution

It introduces the effects of chiral 3NF into the Melbourne g-matrix interaction and analyzes their impact on scattering observables at 65 MeV.

Findings

Chiral 3NF reduces the attraction of the folding potential.

Chiral 3NF increases the absorptive part of the potential.

Effects are subtle at forward angles but significant at backward angles.

Abstract

We investigate the roles of chiral three-nucleon force (3NF) in nucleon-nucleus elastic scattering, using the standard framework based on the Brueckner-Hartree-Fock method for nuclear matter and the $g$-matrix folding model for the nucleon-nucleus scattering. In nuclear matter, chiral 3NF at NNLO level (mainly the 2$\pi$-exchange diagram) makes the single particle potential less attractive for the singlet-even channel and more absorptive for the triplet channels. The single-particle potential calculated from chiral two-nucleon force (2NF) at N$^{3}$LO level is found to be close to that from Bonn-B 2NF. The Melbourne $g$-matrix interaction is a practical effective interaction constructed by localizing the $g$-matrices calculated from Bonn-B 2NF. We then introduce the chiral-3NF effects to the local Melbourne $g$-matrix interaction. For nucleon-nucleus elastic scattering on various targets at 65 MeV, chiral 3NF makes the folding potential less attractive and more absorptive. The novel property for the imaginary part is originated in the enhancement of tensor correlations due to chiral 3NF. The two effects are small for differential cross sections and vector analyzing powers at the forward and middle angles where the experimental data are available. If backward measurements are done, the data will reveal the effects of chiral 3NF.