Two-Component Dark Matter with an SU(2) Dark Sector

TL;DR

The paper introduces a non-Abelian dark sector based on $SU(2)_{D}$ that is spontaneously broken to a residual $Z_{3}$ symmetry, guaranteeing DM stability. A Higgs-portal connects the dark sector to the Standard Model through mixing between the SM Higgs and the dark singlet, producing two DM components: the charged gauge bosons $X^{\pm}$ and the lighter neutral states $\rho_{1}^{(*)}$. The authors compute relic densities by solving Boltzmann equations including annihilation, semi-annihilation, and conversion processes, and confront the model with perturbativity, unitarity, vacuum stability, Higgs phenomenology, direct and indirect detection, dark radiation, and halo ellipticity constraints, identifying viable regions and two benchmark points BP1 and BP2. They find that substantial parameter space remains viable, with distinct predictions for direct detection cross sections and potential indirect detection signals, and with clear implications for future DM experiments. Overall, the work demonstrates that a two-component DM framework with a non-Abelian dark sector and Higgs portal can satisfy current constraints while offering testable signatures at upcoming searches.

Abstract

We propose an extension to the standard model incorporating a dark sector with a non-Abelian SU(2) gauge symmetry. The model yields stable dark matter candidates, protected by a residual $Z_3$ symmetry arising after the spontaneous symmetry breaking. The dark sector interacts with the SM via a Higgs portal, facilitated from mixing between the SM Higgs doublet and a dark scalar singlet. The model features two distinct DM components. We analyze theoretical and experimental constraints, including perturbativity, unitarity, vacuum stability, dark matter relic density, direct detection, indirect detection, Higgs invisible decays, dark radiation, and ellipticity. Our findings identify viable parameter spaces that satisfy these constraints, as exemplified by two benchmark points.

Figures (8)

• Figure 1: The Feynman diagrams of DM annihilation processes. The relevant processes are shown in Eq. (\ref{['annihilation processes']}).
• Figure 2: DM semi-annihilation processes in the model.
• Figure 3: The Feynman diagrams for the DM conversion processes $\rho_{1}+\rho_{1}^{*}\rightarrow X^{+}+X^{-}$, the reverse processes can be obtained by exchanging the initial and final states.
• Figure 4: Left panel: The DM relic density versus the value of the dark sector coupling $g_{D}$. The color bar on the right side represents the DM mass $m_{\rho_1}$. The red line refers to the relic density observed by the PLANCK. Right panel: Collections of points filtered by the observed relic density. The gray line represents the $m_{X^{\pm}}=m_{\rho_1}$ case.
• Figure 5: Feynman diagrams for the Higgs invisible decay to the dark photons.