Abstract
We consider the implications of a shared production mechanism between the baryon asymmetry of the universe and the relic abundance of dark matter, that does not result in matching asymmetries. We present a simple model within a two sector leptogenesis framework, in which right handed sterile neutrinos decay out of equilibrium to both the Standard Model and the dark sector, generating an asymmetry in one and populating the other. This realization naturally accommodates light dark matter in the keV mass scale and above. Interactions in the dark sector may or may not cause the sector to thermalize, leading to interesting phenomenological implications, including hot, warm or cold thermal relic dark matter, while evading cosmological constraints. Under minimal assumptions the model provides a novel non-thermal production mechanism for sterile neutrino dark matter and predicts indirect detection signatures which may address the unexplained 3.5 keV line observed in various galaxy clusters.
Highlights
The existence of dark matter (DM), the baryon asymmetry of the universe and neutrino masses are major observational evidence for physics beyond the standard model (SM)
We find that a shared production mechanism for leptogenesis and symmetric dark matter yields a relic abundance of dark matter that depends on several main factors, namely, the branching fraction to the hidden sector, the decay rate of the heavy right-handed neutrinos, and the number of d.o.f. in the hidden sector
The ratio of dark matter number density to the baryon number density is rather sensitive to the model parameters, thereby accommodating a wide range of dark matter masses
Summary
The existence of dark matter (DM), the baryon asymmetry of the universe and neutrino masses are major observational evidence for physics beyond the standard model (SM). Since the production of an asymmetry requires CP violation and is loop suppressed, relaxing the asymmetric requirement in the dark sector generically results in a tree level enhancement in production, leading to nDM ≫ nB and mDM ≪ mproton. We consider the case where Yukawa interactions between the sterile neutrinos and the SM dynamically trigger leptogenesis at early epochs of the universe, and the sterile neutrino decays to the DM sector produce a relic abundance of symmetric dark matter.
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