Delta-excitations and the three-nucleon force

TL;DR

This paper investigates the role of Delta-resonances in the three-nucleon force within chiral effective field theory, highlighting the dominant two-pion exchange contribution and analyzing isospin-breaking effects including delta mass splittings.

Contribution

It provides the first analysis of delta quartet mass splittings and clarifies the leading contributions to three-nucleon forces involving Delta-resonances.

Findings

The dominant three-nucleon force involving Deltas is the two-pion exchange diagram.

Isospin-breaking corrections due to Deltas are small, around a few keV.

The first analysis of delta quartet mass splittings in chiral EFT is presented.

Abstract

We study the three-nucleon force in chiral effective field theory with explicit Delta-resonance degrees of freedom. We show that up to next-to-next-to-leading order, the only contribution to the isospin symmetric three-nucleon force involving the spin-3/2 degrees of freedom is given by the two-pion-exchange diagram with an intermediate delta, frequently called the Fujita-Miyazawa force. We also analyze the leading isospin-breaking corrections due to the delta. For that, we give the first analysis of the delta quartet mass splittings in chiral effective field theory. The charge-symmetry breaking three-nucleon force due to an intermediate delta excitation is small, of the order of a few keV.