Particle Physics Catalysis of Thermal Big Bang Nucleosynthesis

Abstract

We point out that the existence of metastable, $\ensuremath{\tau}>{10}^{3}\text{ }\text{ }\mathrm{s}$, negatively charged electroweak-scale particles (${X}^{\ensuremath{-}}$) alters the predictions for lithium and other primordial elemental abundances for $A>4$ via the formation of bound states with nuclei during big bang nucleosynthesis. In particular, we show that the bound states of ${X}^{\ensuremath{-}}$ with helium, formed at temperatures of about $T={10}^{8}\text{ }\text{ }\mathrm{K}$, lead to the catalytic enhancement of $^{6}\mathrm{Li}$ production, which is 8 orders of magnitude more efficient than the standard channel. In particle physics models where subsequent decay of ${X}^{\ensuremath{-}}$ does not lead to large nonthermal big bang nucleosynthesis effects, this directly translates to the level of sensitivity to the number density of long-lived ${X}^{\ensuremath{-}}$ particles ($\ensuremath{\tau}>{10}^{5}\text{ }\text{ }\mathrm{s}$) relative to entropy of ${n}_{{X}^{\ensuremath{-}}}/s\ensuremath{\lesssim}3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$, which is one of the most stringent probes of electroweak scale remnants known to date.