Complex scalar dark matter with effective Higgs portals beyond radiation domination

TL;DR

This paper explores how extending the Higgs-portal model with effective operators and considering non-standard cosmological histories can reconcile complex scalar dark matter with experimental constraints, highlighting new viable parameter regions.

Contribution

It introduces an effective field theory approach to complex scalar dark matter production beyond radiation domination, identifying additional viable parameter spaces during reheating.

Findings

Reheating scenarios allow for viable dark matter relic abundance regions.

Dimension-5 Higgs-portal operators are constrained by relic density and indirect detection.

Collider production cross sections are analyzed for future detection prospects.

Abstract

The increasingly stringent bounds on the Higgs-portal coupling, arising from dark matter (DM) direct-detection searches, confront the minimal renormalizable complex scalar DM scenario with thermal production, where freeze-out occurs in the standard radiation-dominated era. This limitation can be alleviated by introducing a dimension-5 Higgs-portal operator in the minimal renormalizable complex scalar DM model and/or by modifying the standard cosmological history of the Universe. In this article, we analyze complex scalar DM production in both the reheating and radiation-dominated epochs within an effective field theory (EFT) framework. While both scenarios exhibit sizeable regions of parameter space consistent with existing constraints, freeze-out during reheating opens up additional viable regions that are otherwise ruled out by DM overabundance in the radiation-dominated scenario. Notably, the renormalizable Higgs-portal coupling is constrained by relic density, direct- and indirect-detection limits, whereas the EFT coupling associated with the dimension-5 operator is constrained by relic density and indirect-detection bounds arising from DM semi-annihilation. We further study the production cross section of complex scalar DM at hadron and lepton colliders.