Two dark matter candidates: The case of inert doublet and singlet scalars

G Bélanger,A Mjallal,A Pukhov

doi:10.1103/physrevd.105.035018

Abstract

We consider a multi-component dark matter model where the dark sector contains a scalar doublet and a complex scalar singlet. We impose a discrete $Z_4$ symmetry to ensure such that the lightest component of the doublet, $\tilde{A}$, and the singlet, $\tilde{S}$, are both stable. Interactions between the dark sectors impact significantly dark matter observables, they allow in particular to significantly relax the direct detection constraints on the model. To determine the parameter space that satisfies relic density, theoretical and collider constraints as well as direct and indirect detection limits, we perform two separate scans, the first includes the full parameter space of the model while the second is dedicated to scenarios with a compressed inert doublet spectrum. In the first case we find that the singlet is generally the dominant dark matter component while in the compressed case the doublet is more likely to be the dominant dark matter component. In both cases we find that the two dark matter particles can have masses that ranges from around $m_h/2$ to over the TeV scale. We emphasize the interplay between cosmological astrophysical and collider constraints and show that a large fraction of the parameter space that escapes current constraints is within the sensitivity reach of future detectors such as XENON-nT, Darwin or CTA. Important collider signatures are mostly found in the compressed spectrum case with the possibility of probing the model with searches for heavy stable charged particles and disappearing tracks. We also show that semi-annihilation processes such as $\tilde{S}\tilde{S}\to \tilde{A}Z$ could give the dominant signature in indirect detection searches.

Highlights

The hypothesis that a new weakly interacting particle at the electroweak scale could explain dark matter (DM) has been subjected to a host of experimental tests both in astroparticle and particle physics [1–9]
To determine the parameter space of the model compatible with all current theoretical and experimental constraints, we have performed random scans over the masses and couplings in Eq (3), first using a wide range for all parameters and in the second case restricting to the region where the doublet is nearly degenerate in mass
Combining the dark matter sectors of the IDM and singlet model and allowing interactions between the dark sectors opens up significantly the possibility for DM compatible with stringent relic density and direct detection constraints

Summary

Introduction

The hypothesis that a new weakly interacting particle at the electroweak scale could explain dark matter (DM) has been subjected to a host of experimental tests both in astroparticle and particle physics [1–9]. One of the most attractive features of these scenarios, beyond their theoretical motivation, is the strong correlation between DM production in the early Universe and DM signatures in direct detection (DD), indirect detection (ID), and at colliders These experimental searches have in recent years severely restricted the parameter space of typical weakly interacting massive particles (WIMP) models [10,11]. While the searches for WIMPs continue in order to cover as much as possible the large theoretical space of DM models, at the same time many more avenues are being explored for DM candidates [12] These include extending the range of DM masses from the subGeV [13] to the multiTeV regions [14] or of interaction strengths from feebly [15–17] to strongly interacting [18–21].

Objectives

Results

Conclusion