Non-Thermal Cosmic Rays During Big Bang Nucleosynthesis to Solve the Lithium Problem

TL;DR

This paper proposes that non-thermal cosmic rays during Big Bang nucleosynthesis can resolve the longstanding Lithium Problem by adjusting lithium abundances without significantly affecting deuterium levels.

Contribution

It introduces a novel hypothesis that non-thermal particles during BBN can explain lithium discrepancies, independent of reaction cross-section uncertainties.

Findings

Non-thermal hydrogen and helium can account for Li-7 and Li-6 abundances.

The proposed mechanism minimally impacts deuterium levels.

The hypothesis remains stable across various reaction uncertainties.

Abstract

The discrepancy between the theoretical prediction of primordial lithium abundances and astronomical observations is called the Lithium Problem. We find that extra contributions from non-thermal hydrogen and helium during Big Bang nucleosynthesis can explain the discrepancy, for both Li-7 and Li-6, and will change the deuterium abundance only little. The allowed parameter space of such an amount of non-thermal particles and the energy range is shown. The hypothesis is stable regardless of the cross-section uncertainty of relevant reactions and the explicit shape of the energy spectrum.