Dark matter with exotic mediators: The diquark portal

TL;DR

The paper develops a comprehensive diquark portal for frustrated dark matter (fDM), where DM couples to the Standard Model through a scalar–fermionic mediator pair with renormalizable interactions to two quarks. It systematically catalogs all allowed SM representations of the mediators (color 6, 3, 8, 1 with SU(2)L charges 1, 3, or 2 in certain cases) and identifies two universal decay patterns DPI and DPII that shape collider signatures. The DM phenomenology is explored via annihilation to four quarks in the t-channel, with on-shell mediator production providing the dominant relic-density channel; direct detection is loop-suppressed while indirect detection via Fermi-LAT places nontrivial constraints in parts of parameter space. The work further investigates several realizations, from weak-singlet/triplet mediators to color-octet weak-doublets, including an extended Manohar–Wise model, and demonstrates that TeV-scale mediators yield viable DM phenomenology while offering distinctive LHC final states such as multi-jet and four-top events, motivating Run 3 studies and future portal extensions.

Abstract

In this work we build out complete mediator sectors for models of frustrated dark matter (fDM), a new paradigm in which fermionic dark matter couples to the Standard Model (SM) through a scalar-fermionic mediator pair. The fDM paradigm allows great freedom in the charge assignments of the mediators: it accommodates any representation of the SM gauge group provided that the scalar and fermionic mediators have the same charges. In this paper, we write down all renormalizable models in which the mediator(s) make contact with the SM through pairs of quarks, a model space we refer to as the diquark portal. The mediators in this portal may be singlets, triplets, sextets, or octets of the color group $\mathrm{SU}(3)_{\text{c}}$. The mediators may additionally be in non-trivial representations of the weak group $\mathrm{SU}(2)_{\text{L}}$, including doublet and triplet representations, depending on the mediators' color charge. In addition to writing the complete set of renormalizable Lagrangians, we categorize the general collider phenomenology of the models and discuss pair- and single-production LHC signatures of the mediator sectors.

Figures (12)

• Figure 1: Three-point interaction between dark matter $\chi$, SM fermion $f$, and mediating scalar $\phi$, typical of simplified $t$-channel models. The mediator must carry the quantum numbers of the SM field.
• Figure 2: Example interactions between frustrated DM $\chi$, mediator pair $\{\varphi,\Psi\}$, and (eventually) the Standard Model. The mediators can carry any quantum numbers permitting at least one interaction with SM fields.
• Figure 3: Schematic diagram for Decay Pattern II of a scalar mediator $\varphi$. Such decays may dominate if kinematically open and if the mediator-DM coupling $y_{\chi}$ is sufficiently large.
• Figure 4: Scans of fDM parameter space with weak-singlet mediators showing contours of correct relic abundance, $\Omega h^2 \approx 0.12$ (solid) and indirect-detection limits from Fermi-LAT (dashed). We adopt a uniform benchmark scenario in which the scalar mediator(s) has $m_{\varphi} = 1.15$ TeV and the fermionic mediator(s) has $m_{\Psi} = 1.6$ TeV; this choice puts us in Decay Pattern I. See text for details.
• Figure 5: Scalar mediator pair production via gluon fusion followed by decays according to both decay patterns.