Direct Detection of Non-Chiral Dark Matter

TL;DR

This paper explores the detectability of non-chiral fermion dark matter candidates through future direct detection experiments, highlighting mechanisms that could enable their observation despite challenges at colliders.

Contribution

It identifies viable non-chiral fermion dark matter candidates and analyzes their potential detection via radiative and Higgs-mediated couplings.

Findings

Real non-chiral dark matter may be detected via radiative couplings.

Certain doublet models suppress Z-boson couplings, enabling detection.

Singlet dark matter could be observed through Higgs exchange.

Abstract

Direct detection experiments rule out fermion dark matter that is a chiral representation of the electroweak gauge group. Non-chiral real, complex and singlet representations, however, provide viable fermion dark matter candidates. Although any one of these candidates will be virtually impossible to detect at the LHC, it is shown that they may be detected at future planned direct detection experiments. For the real case, an irreducible radiative coupling to quarks may allow a detection. The complex case in general has an experimentally ruled out tree-level coupling to quarks via Z-boson exchange. However, in the case of two SU(2)_L doublets, a higher dimensional coupling to the Higgs can suppress this coupling, and a remaining irreducible radiative coupling may allow a detection. Singlet dark matter could be detected through a coupling to quarks via Higgs exchange. Since all non-chiral dark matter can have a coupling to the Higgs, at least some of its mass can be obtained from electroweak symmetry breaking, and this mass is a useful characterization of its direct detection cross-section.