Abstract. We explore constraints on multipartite dark matter (DM) framework composed of singlet scalar DM interacting with the Standard Model (SM) through Higgs portal coupling. We compute relic density and direct search constraints including the updated LUX bound for two component scenario with non-zero interactions between two DM components in Z 2 × Z 2 framework in comparison with the one having O(2) symmetry. We point out availability of a significantly large region of parameter space of such a multipartite model with DM-DM interactions.

Abstract:The minimal Higgs portal dark matter model is increasingly in tension with recent results form direct detection experiments like LUX and XENON. In this paper we make a systematic study of simple extensions of the Z 2 stabilized singlet scalar Higgs portal scenario in terms of their prospects at direct detection experiments. We consider both enlarging the stabilizing symmetry to Z 3 and incorporating multipartite features in the dark sector. We demonstrate that in these non-minimal models the interplay of annihilation, co-annihilation and semi-annihilation processes considerably relax constraints from present and proposed direct detection experiments while simultaneously saturating observed dark matter relic density. We explore in particular the resonant semi-annihilation channel within the multipartite Z 3 framework which results in new unexplored regions of parameter space that would be difficult to constrain by direct detection experiments in the near future. The role of dark matter exchange processes within multi-component Z 3 × Z 3 framework is illustrated. We make quantitative estimates to elucidate the role of various annihilation processes in the different allowed regions of parameter space within these models.

We investigate the electroweak vacuum stability in an extended version of the Standard Model that incorporates two additional singlet scalar fields and three right-handed neutrinos. One of these extra scalars plays the role of dark matter, while the other scalar not only helps make the electroweak vacuum stable but also opens up the low-mass window of the scalar singlet dark matter (< 500 GeV). We consider the effect of large neutrino Yukawa coupling on the running of Higgs quartic coupling. We have analyzed the constraints on the model and identified the range of parameter space that is consistent with the neutrino mass, appropriate relic density, and direct search limits from the latest XENON 1T preliminary result as well as realized the stability of the electroweak vacuum up to the Planck scale.

The idea of this work is to investigate the constraints on the dark matter (DM) allowed parameter space from high scale validity (absolute stability of Higgs vacuum and perturbativity) in presence of multi particle dark sector and heavy right handed neutrinos to address correct neutrino mass. We illustrate a simple two component DM model, consisting of one inert SU (2) L scalar doublet and a scalar singlet, both stabilised by additional Z 2 ×Z 2 symmetry, which also aid to vacuum stability. We demonstrate DM-DM interaction helps achieving a large allowed parameter space for both the DM components by evading direct search bound. High scale validity puts further constraints on the model, for example, on the mass splitting between the charged and neutral component of inert doublet, which has important implication to its leptonic signature(s) at the Large Hadron Collider (LHC).

Basic idea of this analysis is to achieve a two-component dark matter (DM) framework composed of a scalar and a fermion, with non-negligible DM-DM interaction contributing to thermal freeze out (hence relic density), but hiding them from direct detection bounds. We therefore augment the Standard Model (SM) with a scalar singlet (S) and three vectorlike fermions: two singlets (χ 1 , χ 2 ) and a doublet (N ). Stability of the two DM components is achieved by a discrete Z 2 × Z 2 symmetry, under which the additional fields transform suitably. Fermion fields having same Z 2 × Z 2 charge (N, χ 1 in the model) mix after electroweak symmetry breaking (EWSB) and the lightest component becomes one of the DM candidates, while scalar singlet S is the other DM component connected to visible sector by Higgs portal coupling. The heavy fermion (χ 2 ) plays the role of mediator to connect the two DM candidates through Yukawa interaction. This opens up a large parameter space for the heavier DM component through DM-DM conversion. Hadronically quiet dilepton signature, arising from the fermion dark sector, can be observed at Large Hadron Collider (LHC) aided by the presence of a lighter scalar DM component, satisfying relic density and direct search bounds through DM-DM conversion. arXiv:1809.07474v2 [hep-ph]