Top-philic dark matter within and beyond the WIMP paradigm

TL;DR

This paper analyzes a top-philic Majorana dark matter model with a colored t-channel mediator, exploring its rich phenomenology, relic density mechanisms, and experimental constraints, especially focusing on light dark matter and conversion-driven freeze-out.

Contribution

It provides a comprehensive analysis of a simple yet phenomenologically rich top-philic dark matter model, including novel freeze-out mechanisms and collider signatures.

Findings

Relic density can be achieved over a wide parameter range.

Conversion-driven freeze-out is a key mechanism testable at the LHC.

Several parameter regions evade current experimental constraints.

Abstract

We present a comprehensive analysis of top-philic Majorana dark matter that interacts via a colored t-channel mediator. Despite the simplicity of the model -- introducing three parameters only -- it provides an extremely rich phenomenology allowing us to accommodate the relic density for a large range of coupling strengths spanning over six orders of magnitude. This model features all `exceptional' mechanisms for dark matter freeze-out, including the recently discovered conversion-driven freeze-out mode, with interesting signatures of long-lived colored particles at colliders. We constrain the cosmologically allowed parameter space with current experimental limits from direct, indirect and collider searches, with special emphasis on light dark matter below the top mass. In particular, we explore the interplay between limits from Xenon1T, Fermi-LAT and AMS-02 as well as limits from stop, monojet and Higgs invisible decay searches at the LHC. We find that several blind spots for light dark matter evade current constraints. The region in parameter space where the relic density is set by the mechanism of conversion-driven freeze-out can be conclusively tested by R-hadron searches at the LHC with 300\,fb$^{-1}$.