Minimal Dark Matter: Generalized Framework and Direct-Detection Sensitivity

TL;DR

This paper develops a generalized framework to accurately calculate nonperturbative effects in minimal dark matter models, assessing their direct-detection prospects and revealing some models may evade detection below the neutrino floor.

Contribution

It introduces a comprehensive method for evaluating nonperturbative effects in extended minimal dark matter models, improving upon previous calculations and exploring detection limits.

Findings

Some mixed multiplet models have signals below the neutrino floor.

The framework corrects previous literature shortcomings.

Testing minimal dark matter requires more than direct detection.

Abstract

Minimal electroweak dark matter models are compelling due to their simplicity, though calculations of their freezeout abundance are complicated by nonperturbative effects due to Sommerfeld enhancement and bound-state formation. It has been shown that all individual multiplet scenarios beyond the doublet lead to direct-detection signals above the neutrino floor and thus within the reach of next-generation experiments. If no signals are found, would minimal dark matter be excluded? Yes for the simplest models, but it has been unknown for the important extension of two multiplets coupled by Higgs interactions (Higgs-coupled minimal dark matter). We present a generalized framework for calculating nonperturbative effects for such models that also covers the case of individual multiplets. In this framework, we calculate nonperturbative effects on freezeout as well as the prospects for direct detection, correcting shortcomings and omissions in the literature. Importantly, for the mixed Majorana (odd) and Dirac (even) multiplet combinations 3M2D, 5M4D, and 7M6D, we find that the predicted direct-detection signals can extend below the neutrino floor. Fully testing minimal dark matter will thus require more than direct-detection experiments.