Ab initio framework for nuclear scattering and reactions induced by light projectiles

A quantitative and predictive microscopic theoretical framework that can describe reactions induced by α particles (⁴He nuclei) and heavier projectiles is currently lacking. Such a framework would contribute to reducing uncertainty in the modeling of stellar evolution and nucleosynthesis and provide the basis for achieving a comprehensive understanding of the phenomenon of nuclear clustering (the organization of protons and neutrons into distinct substructures within a nucleus). We have developed an efficient and general configuration-interaction framework for the description of low-energy reactions and clustering in light nuclei. The new formalism takes full advantage of powerful second-quantization techniques, enabling the description of α-α scattering and an exploration of clustering in the exotic ¹²Be nucleus. We find that the ⁴He(α, α)⁴He differential cross section computed with non-locally regulated chiral interactions is in good agreement with experimental data. Our results for ¹²Be indicate the presence of strongly mixed helium-cluster states consistent with a molecular-like picture surviving far above the ⁶He+⁶He threshold, and reveal the strong influence of neutron decay in both the ¹²Be spectrum and in the ⁶He(⁶He,α)⁸He cross section. We expect that this approach will enable the description of helium burning cross sections and provide insight on how three-nucleon forces influence the emergence of clustering in nuclei.