Abstract
Background: Deuteron-induced nuclear reactions are an essential tool for probing the structure of nuclei as well as astrophysical information such as cross sections. The deuteron-nucleus system is typically described within a Faddeev three-body model consisting of a neutron (), a proton (), and the target nucleus () interacting through pairwise phenomenological potentials. While Faddeev techniques enable the exact description of the three-body dynamics, their predictive power is limited in part by the omission of irreducible neutron-proton-nucleus three-body force ( 3BF).
Purpose: Our goal is to quantify systematic uncertainties stemming from the reduction of deuteron-nucleus () dynamics to a picture of three pointlike nuclear clusters interacting via pairwise nucleon-nucleus forces, using as testing grounds scattering and the ground state. We particularly focus on quantifying uncertainties arising from the full antisymmetrization of the ()-body system with the target nucleus fixed in its ground state.
Methods: We adopt the ab initio no-core shell model coupled with the resonating group method (NCSM/RGM) to compute microscopic and interactions, and use them in a three-body description of the system by means of momentum-space Faddeev-type equations. Simultaneously, we also carry out ab initio calculations of scattering and ground state by means of six-body NCSM/RGM calculations to serve as a benchmark for the three-body model predictions given by the Faddeev calculations.
Results: By comparing the Faddeev and NCSM/RGM results, we show that the irreducible 3BF has a non-negligible effect on bound state and scattering observables alike. Specifically, the Faddeev approach yields a ground state that is approximately 600 keV shallower than the one obtained with the NCSM/RGM. Additionally, the Faddeev calculations for scattering yield a resonance that is located approximately 400 keV higher in energy compared to the NCSM/RGM result. The shape of the angular distributions computed using the two approaches also differ, owing to the discrepancy in the predictions of the resonance energy.
Conclusions: The Faddeev three-body model predictions for scattering and using microscopic and potentials differ from those computed microscopically with the NCSM/RGM. These discrepancies are due to the 3BF, which arises from two-nucleon exchange terms in the microscopic interaction and are not accounted for in the three-body model Faddeev calculations. This study lays the foundation for future parametrizations of the 3BF due to Pauli exclusion principle effects in improved three-body calculations of deuteron-induced reactions.
2 More- Received 16 August 2022
- Accepted 22 December 2022
DOI:https://doi.org/10.1103/PhysRevC.107.014315
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