We consider fermionic and scalar dark matter (DM) candidates that couple predominantly to third-generation Standard Model fermions, describing their interactions within an effective field theory framework. We show that current direct-detection constraints on these interactions are more than an order of magnitude weaker than those for flavor-universal couplings: effective scales in the few-TeV range remain allowed by existing data, leaving open the possibility of a connection between this type of new physics and a solution to the electroweak hierarchy problem. Imposing the observed relic abundance from thermal freeze-out within the same effective theory, a well-defined region for a fermionic DM candidate with mass in the 1-2 TeV range emerges. Notably, this region will be fully probed by upcoming direct-detection experiments. Finally, we show that additional parameter space for both fermion and scalar cases can be recovered by going beyond the effective theory, through the introduction of a suitable vector mediator enabling resonant DM annihilation.
Demetriou et al. (Tue,) studied this question.