Singlet-doublet Majorana dark matter and neutrino mass in a minimal type-I seesaw scenario

Abstract

In a bid to simultaneous explanation of dark matter (DM) and tiny but non-zero masses of left-handed neutrinos, we propose a minimal extension of the Standard Model (SM) by a vector-like fermion doublet and three right handed (RH) singlet neutrinos. The DM arises as a mixture of the neutral component of the fermion doublet and one of the RH neutrinos, both assumed to be odd under an additional 𝒵2 symmetry. As a result, the DM emerges to be a dominantly Majorana particle and escapes from Z-mediated direct search constraints to mark a significant difference from singlet-doublet Dirac DM. The other two 𝒵2 even heavy RH neutrinos give rise masses and mixing of light neutrinos via Type-I Seesaw mechanism. The particle content automatically allows us to extend the model by a gauged U(1)B-L symmetry, which is anomaly free and brings an additional portal between DM and SM particles. Relic density and direct search allowed parameter space for both the cases are investigated through detailed numerical scan, while collider search strategies are also indicated.

Lepton Anomalous Magnetic Moment with Singlet-Doublet Fermion Dark Matter in Scotogenic $U(1)_{L_μ-L_τ}$ Model

“…As the minimal model described above can not explain the electron and muon (g − 2) data simultaneously while being in agreement with CLFV constraints, we extend the model by introducing a vector like fermion doublet Ψ T = (ψ 0 , ψ − ) ∼ (1, 2, − 1 2 , 0) which is also odd under the Z 2 symmetry, but has vanishing U (1) Lµ−Lτ charge. Since there exists a RHN which also has vanishing U (1) Lµ−Lτ charge, this leads to the possibility of singlet-doublet fermion dark matter [61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78].…”

“…It should be noted that we have considered other Z 2 particles not part of the mass matrix (25) above to be much heavier. For a detailed analysis of singlet-doublet Majorana DM, one may refer to the recent work [78].…”

“…While a large sin θ (upto 0.6) is allowed in the present case simultaneously by relic as well as direct search, only upto sin θ ∼ 0.01 is allowed in case of singlet-doublet Dirac fermion DM. The cross section per nucleon for the spinindependent (SI) DM-nucleon interaction is then given by [78]…”

“…We then consider an extension of the minimal scotogenic L µ − L τ model with a Z 2 -odd vector like lepton doublet with vanishing U (1) Lµ−Lτ charge. Due to the possibility of vector like lepton doublet coupling with one of the RHNs, it gives rise to a singlet-doublet fermion DM scenario studied extensively in the literature [61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79]. We show that the inclusion of this vector like lepton doublet which couples only to electrons and one of the RHNs due to vanishing U (1) Lµ−Lτ charge, the observed (g −2) e can be generated due to chiral enhancement in the one-loop diagram mediated by charged scalar and fermions.…”

Distinguishing two dark matter component particles at $e^+e^-$ colliders

“…Let us now turn to fermion DM component. The minimal renormalizable Lagrangian for the fermion dark sector (FDM) having one vector like doublet (Ψ) and one right handed singlet (χ R ) reads [63]:…”