# Roles of $^7$Be$(n,p)^7$Li resonances in big bang nucleosynthesis with time-dependent quark mass and Li reduction by a heavy quark mass

## TL;DR

This study examines how variations in the quark mass during the early Universe influence nuclear reaction rates, especially 7Be(n,p)7Li, affecting primordial element abundances and potentially resolving the lithium problem.

## Contribution

It introduces a detailed analysis of 8Be resonances' effects on BBN with a time-dependent quark mass, highlighting the impact on lithium abundance.

## Key findings

- Resonance at 0.33 MeV significantly enhances reaction rates.
- Negative quark mass variation reduces 7Li abundance.
- Quark mass variation of (4--8)×10^{-3} aligns lithium predictions with observations.

## Abstract

Big bang nucleosynthesis (BBN) has been used as a probe of beyond-standard physics in the early Universe, which includes a time-dependent quark mass m_q. We investigate effects of a quark mass variation delta m_q on the cross sections of the 7Be(n, p)7Li reaction and primordial light element abundances taking into account roles of 8Be resonances in the reaction during BBN. This resonant reaction has not been investigated although behaviors of low-lying resonances are not trivial. It is found that a resonance at the resonance energy E_r=0.33 MeV enhances the reaction rate and lowers the 7Li abundance significantly when the quark mass variation is negative. Based upon up-to-date observational limits on primordial abundances of D, 4He and Li, the quark mass variation in the BBN epoch are derived. In a model in which the resonance energies of the reactions 3He(d, p)4He and 3H(d, n)4He are insensitive to the quark mass, we find that the Li abundance can be consistent with observations for delta m_q/m_q = (4--8) times 10^{-3}.