Connecting $t$-channel Dark Matter Models to the Standard Model Effective Field Theory

TL;DR

This paper links t-channel dark matter models with leptons to the Standard Model Effective Field Theory by computing Wilson coefficients at one loop and analyzing constraints from relic density, SMEFT fits, and direct detection.

Contribution

It provides the first detailed one-loop matching of t-channel dark matter models to SMEFT and explores phenomenological constraints in a compressed spectrum scenario.

Findings

SMEFT bounds can constrain dark matter masses above 0.5 TeV.

Loop-suppressed SMEFT constraints are significant for certain parameter ranges.

Relic density calculations include coannihilations, Sommerfeld, and bound-state effects.

Abstract

We investigate the connection between simplified dark matter models featuring a $t$-channel scalar mediator and the Standard Model Effective Field Theory (SMEFT). We focus on scenarios with fermionic dark matter interacting with leptons, under the assumption of Minimal Flavor Violation. The dimension-six SMEFT Wilson coefficients are computed in the Warsaw basis at one loop, with the aid of Matchete. Assuming a compressed mass spectrum for the dark matter and the mediator, we incorporate coannihilations, Sommerfeld enhancement, and bound-state effects in the relic density calculation. We then analyze the interplay between the dark matter energy density, global SMEFT fits, and direct detection constraints. Our results show that SMEFT bounds, though loop-suppressed, can meaningfully constrain the parameter space for $m_\chi \gtrsim 0.5$ TeV and $\mathcal{O}(1)$ portal couplings.