Destruction of 7Be in big bang nucleosynthesis via long-lived sub-strongly interacting massive particles as a solution to the Li problem

Abstract

We identify reactions which destroy 7Be and 7Li during big bang nucleosynthesis (BBN) in the scenario of BBN catalyzed by a long-lived sub-strongly interacting massive particle (sub-SIMP or X particle). The destruction associated with non radiative X captures of the nuclei can be realized only if the interaction strength between an X particle and a nucleon is properly weaker than that between two nucleons to a degree depending on the mass of X. Binding energies of nuclei to an X particle are estimated taking the mass and the interaction strength to nuclei of the X as input parameters. Nuclear reaction rates associated with the X are estimated naively, and adopted in calculating evolutions of nuclear abundances. We suggest that the 7Li problem, which might be associated with as-yet-unrecognized particle processes operating during BBN, can be solved if the X particle interacts with nuclei strongly enough to drive 7Be destruction but not strongly enough to form a bound state with 4He of relative angular momentum L=1. Justifications of this scenario by rigorous calculations of reaction rates using quantum mechanical many-body models are highly desirable since this result involves many significant uncertainties.