Interplay between Electroweak Symmetry Breaking and Dark Matter Relic Density

TL;DR

Electroweak symmetry breaking (EWSB) modifies DM masses and interactions during the early Universe, which can significantly affect relic-density calculations for DM that freezes out before EWSB. The authors introduce an improved relic-density framework that treats pre-EWSB (unbroken phase) and post-EWSB (broken phase) epochs separately and quantify deviations from the standard broken-phase approach using a model-independent measure. Applying this to a two-singlet scalar model shows that neglecting EWSB can misclassify viable parameter regions, while the improved method can reopen or further constrain them, depending on the interplay between annihilation channels and mass shifts across EWSB. The findings have implications for TeV-scale DM searches, direct-detection prospects, and potential collider tests, and provide analytic tools to assess EWSB-induced effects on DM relic density in general freeze-out scenarios.

Abstract

Models of Dark Matter must contend with the fact that the presence of electroweak symmetry breaking along the thermal evolution of the Universe modifies the masses, interactions and, thus, the thermally averaged cross sections. We study in detail the impact of taking (not taking) the presence of the electroweak symmetry breaking into account in the calculations of the Dark Matter relic density, providing a model-independent measure of such differences. By focusing on a particular model, we show that ignoring this effect can lead to the inclusion (exclusion) of wrong (viable) regions of parameter space.

Figures (7)

• Figure 1: Annihilation channels of scalar particles before EWSB
• Figure 2: Dark matter annihilation channels after EWSB.
• Figure 3: Relative deviation between approaches ($\delta\Omega h^2$) against $m_\chi$. Red points have $\Omega h^2 |_I \approx 0.120$. Green points have $\Omega h^2 |_I \approx 0.120$ and are allowed by Direct Detection constraints.
• Figure 4: Sign of $\delta \Omega h^2$ plotted in the $\alpha-\beta$ plane.
• Figure 5: Left: A point allowed in the standard approach, but the improved approach forbids it. Right: A point discarded by the standard formalism but allowed in the improved approach.