Role of the total isospin 3/2 component in three-nucleon reactions

TL;DR

This paper investigates the impact of the isospin T=3/2 component in three-nucleon reactions, highlighting its significance in breakup processes and minimal effect in elastic scattering, using chiral and phenomenological potentials.

Contribution

It demonstrates the importance of including the T=3/2 isospin component in three-nucleon reaction calculations, especially for breakup observables, and compares different nuclear force models.

Findings

T=3/2 component is crucial for breakup reactions.

Elastic scattering is insensitive to T=3/2 contributions.

Charge-independence breaking effects are modeled effectively with the 2/3-1/3 rule.

Abstract

We discuss the role of the three-nucleon isospin T=3/2 amplitude in elastic neutron-deuteron scattering and in the deuteron breakup reaction. The contribution of this amplitude originates from charge-independence breaking of the nucleon-nucleon potential and is driven by the difference between neutron-neutron (proton-proton) and neutron-proton forces. We study the magnitude of that contribution to the elastic scattering and breakup observables, taking the locally regularized chiral N4LO nucleon-nucleon potential supplemented by the chiral N2LO three-nucleon force. For comparison we employ also the Av18 nucleon-nucleon potential combined with the Urbana IX three-nucleon force. We find that the isospin T=3/2 component is important for the breakup reaction and the proper treatment of charge-independence breaking in this case requires the inclusion of the 1S0 state with isospin T=3/2. For neutron-deuteron elastic scattering the T=3/2 contributions are insignificant and charge-independence breaking can be accounted for by using the effective t-matrix generated with the so-called "2/3-1/3" rule.