Probing the sterile neutrino portal to Dark Matter with $\gamma$ rays

TL;DR

This paper explores how sterile neutrinos could connect dark matter to the Standard Model and explains the Galactic Center gamma-ray excess through dark matter annihilations involving sterile neutrinos, fitting observational data well.

Contribution

It demonstrates that sterile neutrino portal models can account for the gamma-ray excess with specific dark matter and sterile neutrino mass ranges, consistent with current observational constraints.

Findings

Sterile neutrino portal provides a good fit to the gamma-ray excess (p-value 0.78).

Dark matter masses between 40-80 GeV fit the excess data.

Constraints from dwarf spheroidal galaxies and AMS-02 anti-proton data are compatible with the model.

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 $\gamma$-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 $\gamma$-ray flux, for DM masses in the range (40-80) GeV and sterile neutrino masses 20 GeV $\lesssim M_N < M_{DM}$. 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 $\sim$ 50 GeV (90 GeV), for sterile neutrino masses $M_N \lesssim M_{DM}$ ($M_N \ll M_{DM}$). We also estimate the impact of AMS-02 anti-proton data on this scenario.