Constraints on the Variation of the QCD Interaction Scale $\Lambda_{\text{QCD}}$

TL;DR

This paper investigates possible variations in the QCD scale over time, using atomic clocks, natural reactors, nuclear clocks, quasar spectra, and nucleosynthesis data to set limits on its change rate.

Contribution

It provides the first comprehensive constraints on the time variation of the QCD scale from multiple experimental and observational sources.

Findings

Atomic clock comparisons limit
.1 imes 10^{-17} yr^{-1} for ot{\u03bb}_{QCD} / b{bb}_{QCD}

Oklo reactor data constrains b{bb}_{QCD} variation to less than 2 7 over 1.8 billion years

Proposed nuclear clock could amplify detection sensitivity by four orders of magnitude

Abstract

Laboratory and astrophysical tests of ''constant variation'' have so far concentrated on the dimensionless fine-structure constant $\alpha$ and on the electron or quark mass ratios $X_{e,q}=m_{e,q}/\Lambda_{\text{QCD}}$, treating the QCD scale $\Lambda_{\text{QCD}}$ as unchangeable. Certain beyond Standard Model frameworks, most notably those with a dark matter or dark energy scalar field $\phi$ coupling with the gluon field, would make $\Lambda_{\text{QCD}}$ itself time dependent while leaving $\alpha$ and the electron mass untouched. Under the minimal assumption that this gluonic channel is the sole $\phi$ interaction, we recast state-of-the-art atomic clock comparisons into $\dot{\Lambda}_{\text{QCD}}/\Lambda_{\text{QCD}}=(3.2 \pm 3.5) \times 10^{-17} \ \text{yr}^{-1}$ limits, translate the isotope yields of the 1.8-Gyr-old Oklo natural reactor into a complementary geophysical limit of $|\delta\Lambda_{\text{QCD}}/\Lambda_{\text{QCD}}|<2\times10^{-9}$ over that time span, corresponding to the linear drift limit $|\dot{\Lambda}_{\text{QCD}}/\Lambda_{\text{QCD}}|<1\times10^{-18} \text{yr}^{-1}$, and show that the proposed $8.4$ eV $^{229}$Th nuclear clock would amplify a putative $\Lambda_{\text{QCD}}$ drift by four orders of magnitude compared with present atomic clocks. We also obtain constraints from quasar absorption spectra and Big Bang Nucleosynthesis data.