Singlet-doublet fermion and triplet scalar dark matter with radiative neutrino masses

Abstract

We present a detailed study of a combined singlet-doublet fermion and triplet scalar model for dark matter. These models have only been studied separately in the past. Together, they form a simple extension of the Standard Model that can account for dark matter and explain the existence of neutrino masses, which are generated radiatively. This holds even if singlet-doublet fermions and triplet scalars never contribute simultaneously to the dark matter abundance. However, this also implies the existence of lepton flavour violating processes. In addition, this particular model allows for gauge coupling unification. The new fields are odd under a new Z 2 symmetry to stabilise the dark matter candidate. We analyse the dark matter, neutrino mass and lepton flavour violation aspects both separately and in conjunction, exploring the viable parameter space of the model. This is done using a numerical random scan imposing successively the neutrino mass and mixing, relic density, Higgs mass, direct detection, collider and lepton flavour violation constraints. We find that dark matter in this model is fermionic for masses below about 1 TeV and scalar above. The narrow mass regions found previously for the two separate models are enlarged by their coupling. While coannihilations of the weak isospin partners are sizeable, this is not the case for fermions and scalars despite their often similar masses due to the relatively small coupling of the two sectors, imposed by the small neutrino masses. We observe a high degree of complementarity between direct detection and lepton flavour violation experiments, which should soon allow to fully probe the fermionic dark matter sector and at least partially the scalar dark matter sector.

FIMP DM in the Extended Hyperchargeless Higgs Triplet Model

“…We impose a discrete Z 2 symmetry on this model such that the scalar triplet and vector-like fermions are odd (Ψ BSM → −Ψ BSM ), whereas the SM fields are even (Ψ SM → Ψ SM ) under this transformation. The extra scalar triplet consists of a pair of singly-charged fields H ± and a CP -even neutral scalar field H. The doublet and triplet scalar are conventionally written as [43,66,67]…”

A radiative seesaw model with GeV singlet-doublet fermion and TeV triplet scalar dark matter

“…Here we present a recent study of a model with singlet-doublet fermions and triplet scalars [11], dubbed T1-3-B with α = 0 in the classification scheme cited above. The new fields and their quantum numbers in this model are shown in Tab.…”

minimal-lagrangians: Generating and studying dark matter model Lagrangians with just the particle content

“…For example, the model T1-3-B, which is studied for α = 0 in [11], is defined as BSMModel('T1-3-B', ( FermionField("Ψ", 1, Y= 0), FermionField("ψ'", 2, Y= 1), ScalarField ("φ", 3, Y= 0), FermionField("ψ", 2, Y=-1), ), (0, 2)), # α = -2 is equivalent to α = 2…”

“…Together, these programs form a tool chain which, after specifying a model's field content, largely automates the programmatic implementation of the model's details and rapidly yields executable code to calculate physical observables (see section 6). An example making use of this tool chain is the analysis of the model T1-3-B (α = 0) performed in [11].…”