Quark mass variation constraints from Big Bang nucleosynthesis

TL;DR

This paper investigates how variations in quark masses during Big Bang nucleosynthesis affect light element abundances, using lattice QCD and effective field theories to derive model-independent constraints.

Contribution

It provides the first model-independent bounds on quark mass variations during BBN by linking particle physics to cosmological observations.

Findings

Helium-4 abundance constrains quark mass variation to -1% to 0.7%

Deuterium abundance variations can be offset by baryon-to-photon ratio changes

WMAP data further tightens quark mass variation bounds

Abstract

We study the impact on the primordial abundances of light elements created by a variation of the quark masses at the time of Big Bang nucleosynthesis (BBN). In order to navigate through the particle and nuclear physics required to connect quark masses to binding energies and reaction rates in a model-independent way, we use lattice QCD data and a hierarchy of effective field theories. We find that the measured Helium-4 abundances put a bound of -1 % <~ d m_q/m_q <~ 0.7 % on a possible variation of quark masses. The effect of quark mass variations on the deuterium abundances can be largely compensated by changes of the baryon-to-photon ratio eta. Including bounds on the variation of eta coming from WMAP results and adding some additional assumptions further narrows the range of allowed values of d m_q/m_q.