Calculations of radiative capture and pair production for the ⁸Be composite system

Through first-principles calculations of ⁷Li(p, γ)⁸Be and ⁷Li(p, e⁺e^-)⁸Be capture, we examine the nuclear processes related to the ATOMKI anomaly (which posits the existence of a new boson with a mass of 17 MeV). We calculate the energy and decay of the relevant 1⁺ resonances in ⁸Be.

We apply the no-core shell model with continuum technique to investigate reactions involving both p+⁷Li and n+⁷Be with ⁸Be as the composite system. This method enables accurate description of both bound states and the continuum using chiral nucleon-nucleon and three-nucleon forces as input. We report phase-shifts and cross-sections for a suite of scattering and reaction processes.