The third-generation-philic WIMP: an EFT analysis
PMC12343742
· 10.1140/epjc/s10052-025-14580-5
Gap Declaration
Although loop suppression weakens the direct-detection reach, it is precisely this suppression that enables an important shift in perspective: if dark matter couples predominantly to third-generation fermions, then the scale of new physics can naturally lie in the few TeV region. This stands in contrast to scenarios where dark matter couples directly to light quarks, which are subject to stringent bounds pushing the new physics scale up to TeV. Thus, the assumption of DM coupled mainly to the third-generation provides a viable path to lower-scale new physics, within reach of current and future experiments. Most importantly, this hypothesis, which is theoretically well motivated, leaves open the possibility of a connection between the DM problem and the electroweak hierarchy problem, as in the original spirit of the WIMP paradigm. From the relic-abundance perspective, we have shown that imposing the observed relic abundance from thermal freeze-out, within the EFT approach, leads to strong restrictions of the allowed parameter space.
Abstract
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 up…
Conclusions / Discussion
Conclusions The hypothesis of a multi scale UV completion of the SM, where the first energy threshold above the electroweak scale hosts dynamics coupled mainly to the third-generation of SM fermions, is both theoretically appealing and of great phenomenological interest. In this work, we have investigated how dark matter could fit within this general picture from a general bottom-up EFT perspective. To do so, we have investigated the implications of effective operators coupling dark matter to third-generation SM fermions, both for fermionic and scalar DM candidates, analysing the corresponding bounds from direct detection and relic abundance constraints. From the direct-detection perspective, we have recasted the latest LUX-ZEPLIN limits onto DM-third-generation vector couplings using one-loop matching to light quark currents. Although loop suppression weakens the direct-detection reach, it is precisely this suppression that enables an important shift in perspective: if dark matter couples predominantly to third-generation fermions, then the scale of new physics can naturally lie in the few TeV region. This stands in contrast to scenarios where dark matter couples directly to light…
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