Light Dirac neutrino portal dark matter with observable ΔNeff. Issue 10 (4th October 2021)

• Record Type: Journal Article
• Authors: Biswas, Anirban; Borah, Debasish; Nanda, Dibyendu
• Is Part Of: Journal of cosmology and astroparticle physics. Volume 2021:Issue 10(2021)
• Publication Date: 2021-10-04
• Subjects: dark matter theory -- particle physics - cosmology connection -- cosmology of theories beyond the SM -- neutrino properties; Cosmology -- Periodicals; Astrophysics -- Periodicals; 523.0105
• DOI: 10.1088/1475-7516/2021/10/002
• Languages: English
• ISSNs: 1475-7516

Abstract

Abstract: We propose a Dirac neutrino portal dark matter scenario by minimally extending the particle content of the Standard Model (SM) with three right-handed neutrinos (ν R ), a Dirac fermion dark matter candidate (ψ) and a complex scalar (ϕ), all of which are singlets under the SM gauge group. An additional ℤ4 symmetry has been introduced for the stability of dark matter candidate ψ and also ensuring the Dirac nature of light neutrinos at the same time. Both the right handed neutrinos and the dark matter thermalise with the SM plasma due to a new Yukawa interaction involving ν R, ψ and ϕ while the latter maintains thermal contact via the Higgs portal interaction. The decoupling of ν R occurs when ϕ loses its kinetic equilibrium with the SM plasma and thereafter all three ℤ4 charged particles form an equilibrium among themselves with a temperature TνR . The dark matter candidate ψ finally freezes out within the dark sector and preserves its relic abundance. We have found that in the present scenario, some portion of low mass dark matter ( M ψ ≲ 10 GeV) is already excluded by the Planck 2018 data for keeping ν R s in the thermal bath below a temperature of 600 MeV and thereby producing an excess contribution to N eff . The next generation experiments like CMB-S4, SPT-3G etc. will have the required sensitivities to probe the entire model parameter space of this minimal scenario, especially the low mass range of ψ where direct detection experiments are still not capable enough for detection.