Ab initio many-body calculations of nucleon scattering on 4He, 7Li, 7Be, 12C and 16O

TL;DR

This paper develops an advanced ab initio many-body method to accurately describe nucleon scattering and bound states in light nuclei, predicting new resonances and analyzing nuclear structure with high precision.

Contribution

It introduces an improved NCSM/RGM approach with importance truncation, enabling calculations for nuclei up to mass number 17, including scattering and resonance predictions.

Findings

Predicted low-lying resonances in 8Li and 8B not yet clearly identified experimentally.

Reasonably reproduced low-lying states in 13C.

Identified limitations in describing 17O states without further model improvements.

Abstract

We combine a recently developed ab initio many-body approach capable of describing simultaneously both bound and scattering states, the ab initio NCSM/RGM, with an importance truncation scheme for the cluster eigenstate basis and demostrate its applicability to nuclei with mass numbers as high as 17. Using soft similarity renormalization group evolved chiral nucleon-nucleon interactions, we first calculate nucleon-4He phase shifts, cross sections and analyzing power. Next, we investigate nucleon scattering on 7Li, 7Be, 12C and 16O in coupled-channel NCSM/RGM calculations that include low-lying excited states of these nuclei. We check the convergence of phase shifts with the basis size and study A=8, 13, and 17 bound and unbound states. Our calculations predict low-lying resonances in 8Li and 8B that have not been experimentally clearly identified yet. We are able to reproduce reasonably well the structure of the A=13 low lying states. However, we find that A=17 states cannot be described without an improved treatment of 16O one-particle-one-hole excitations and alpha clustering.