Bridging the $ \mu $Hz gap in the gravitational-wave landscape: unveiling dark baryons

Abstract

We study gravitational waves (GWs) with frequencies in the $\mu$Hz range, which arise from phase transitions related to dark confinement in the context of dark versions of Quantum Chromodynamics. Based on several compelling motivations, we posit that these theories predict the existence of GeV-mass asymmetric dark baryons, akin to ordinary baryons, with the potential to contribute to dark matter. Furthermore, we emphasize the significance of a particular $\mathcal{O}(\text{TeV})$ scale for multiple reasons. First, to account for the similarity in present-day mass densities between dark matter and visible matter, various TeV-scale mechanisms can elucidate the similarities in both their number densities and masses. Moreover, to address the so-called electroweak hierarchy problem, we consider the introduction of either the Composite Higgs or Supersymmetry at around $\mathcal{O}(\text{TeV})$. These mechanisms lead to intriguing TeV collider signatures and the possibility of detecting mHz GWs in future experiments. In summary, this study provides a strong motivation for advancing GW experiments that can bridge the $\mu$Hz frequency gap in the GW spectrum. Additionally, there is a need for the construction of more powerful particle colliders to explore higher energy regimes. In consideration of the possibility to scrutinize these models from various perspectives, we strongly advocate their further development.