Probing the sterile neutrino portal to Dark Matter with γ rays

Abstract

Sterile neutrinos could provide a link between the Standard Model particles and a dark sector, besides generating active neutrino masses via the seesaw mechanism type I. We show that, if dark matter annihilation into sterile neutrinos determines its observed relic abundance, it is possible to explain the Galactic Center γ-ray excess reported by the Fermi-LAT Collaboration as due to an astrophysical component plus dark matter annihilations. We observe that sterile neutrino portal to dark matter provides an impressively good fit, with a p-value of 0.78 in the best fit point, to the Galactic Center γ-ray flux, for DM masses in the range (40-80) GeV and sterile neutrino masses 20 GeV M N < M DM . Such values are compatible with the limits from Fermi-LAT observations of the dwarfs spheroidal galaxies in the Milky Way halo, which rule out dark matter masses below ∼ 50 GeV (90 GeV), for sterile neutrino masses M N M DM (M N M DM ). We also estimate the impact of AMS-02 anti-proton data on this scenario.

A systematic study of hidden sector dark matter: application to the gamma-ray and antiproton excesses

“…As this portal typically involves 3-body boosted decays, we do not include an analysis of this case in our study. We do note, however, that this model has previously been shown to be capable of fitting the Galactic Center gamma-ray excess [35,36,64,66] as well as the cosmic-ray antiproton excess [66].…”

“…In this study, we show that a wide variety of hidden sector dark matter models can simultaneously accommodate both of these excesses (for earlier related work, see refs. [40,[61][62][63][64][65][66]). We attempt to broadly characterize the ingredients of a hidden sector model that would be required in order to (1) produce s-wave annihilation (and thus produce a sufficient number of gamma-rays and anti-protons), (2) have a final state gamma-ray and antiproton spectrum peaked in the energy ranges of the respective excesses, (3) evade current constraints, and (4) achieve kinetic equilibrium in the early Universe.…”

Loop dominated signals from neutrino portal dark matter

“…The exact number of heavy sterile neutrinos is irrelevant for our discussions; hence, we leave it unspecified.2 Scenarios where sterile neutrinos are light enough to be produced directly in dark matter annihilation or decay can also produce interesting dark matter signatures (see, e.g., Refs [6,27,[31][32][33]…”

The dispirited case of gauged U(1)B − L dark matter

“…In this case, the massive pseudoscalar will always decay to light active neutrinos unless m N < m a /2. Therefore, if the annihilation is dominated by χχ → N N the sterile neutrinos will decay to SM particles, and m χ 100 GeV are excluded from dwarf galaxies observations [88][89][90]. Dark matter masses m χ 100 GeV are also excluded from gamma-ray observations in the case that the annihilation is dominated by χχ → a ρ 2 , provided that the sterile neutrinos are light enough, i.e.…”