Primordial beryllium as a big bang calorimeter

TL;DR

This paper explores how primordial beryllium can serve as a sensitive indicator of non-thermal energy injections from decaying particles during nucleosynthesis, providing constraints on new physics models.

Contribution

It introduces a novel method of using primordial beryllium abundance as a calorimeter for early universe energy injections from new physics.

Findings

^9Be production is efficient with energy injections of ~10 MeV per baryon at a few hours after the Big Bang.

Absence of a ^9Be/H plateau down to 10^{-14} constrains models with late-decaying particles.

Primordial beryllium can robustly test physics beyond the Standard Model during nucleosynthesis.

Abstract

Many models of new physics including variants of supersymmetry predict metastable long-lived particles that can decay during or after primordial nucleosynthesis, releasing significant amounts of non-thermal energy. The hadronic energy injection in these decays leads to the formation of ^9Be via the chain of non-equilibrium transformations: Energy_h -> T, ^3He -> ^6He, ^6Li -> ^9Be. We calculate the efficiency of this transformation and show that if the injection happens at cosmic times of a few hours, the release of 10 MeV per baryon can be sufficient for obtaining a sizable ^9Be abundance. The absence of a plateau-structure in the ^9Be/H abundance down to a 10^{-14} level allows one to use beryllium as a robust constraint on new physics models with decaying or annihilating particles.