Abstract
We investigate the feasibility of the indirect detection of dark matter in a simple model using the neutrino portal. The model is very economical, with right-handed neutrinos generating neutrino masses through the Type-I seesaw mechanism and simultaneously mediating interactions with dark matter. Given the small neutrino Yukawa couplings expected in a Type-I seesaw, direct detection and accelerator probes of dark matter in this scenario are challenging. However, dark matter can efficiently annihilate to right-handed neutrinos, which then decay via active-sterile mixing through the weak interactions, leading to a variety of indirect astronomical signatures. We derive the existing constraints on this scenario from Planck cosmic microwave background measurements, Fermi dwarf spheroidal galaxies and Galactic Center gamma-rays observations, and Alpha Magnetic Spectrometer - 02 antiprotons observations, and also discuss the future prospects of Fermi and the Cherenkov Telescope Array. Thermal annihilation rates are already being probed for dark matter lighter than about 50 GeV, and this can be extended to dark matter masses of 100 GeV and beyond in the future. This scenario can also provide a dark matter interpretation of the Fermi Galactic Center gamma ray excess, and we confront this interpretation with other indirect constraints. Finally we discuss some of the exciting implications of extensions of the minimal model with large neutrino Yukawa couplings and Higgs portal couplings.
Highlights
A wide array of gravitational phenomena over a range of cosmological scales strongly support the hypothesis of dark matter (DM) [1,2,3]
This scenario can provide a DM interpretation of the Fermi Galactic center gamma-ray excess, we demonstrate that such an interpretation faces some tension from dwarf spheroidal satellite galaxies and antiproton constraints
We have investigated a simple model of neutrino portal DM, in which the right-handed neutrinos (RHNs) simultaneously generate light neutrino masses via the type-I seesaw mechanism and mediate interactions of DM with the Standard Model (SM)
Summary
A wide array of gravitational phenomena over a range of cosmological scales strongly support the hypothesis of dark matter (DM) [1,2,3]. Thermal relic annihilation rates are already constrained for DM masses below about 50 GeV This scenario can provide a DM interpretation of the Fermi Galactic center gamma-ray excess, we demonstrate that such an interpretation faces some tension from dwarf spheroidal satellite galaxies (dSphs) and antiproton constraints. We describe extensions of this scenario beyond the minimal model, including scenarios with large Yukawa and Higgs portal couplings, and highlight the potentially rich physics implications in cosmology, direct detection, and collider experiments Besides these probes, there is the interesting possibility of a hard gamma-ray spectral feature that arises from the radiative decays of N, which could place complementary constraints in the region mχ ∼ mN, mN ≲ 50 GeV.
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