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In our current understanding of the universe, the fundamental nature of its two most abundant constituents, dark matter (DM) and dark energy (DE), is still a mystery. In particular, despite the plethora of candidates theorized, an experimentally confirmed explanation for the DM puzzle is still missing. Due to the lack of positive evidence in experiments investigating WIMPs, in the last years non-WIMP solutions became more and more appealing. One of such DM candidates is constituted by the sterile neutrino with a mass of O(keV). The simplest mechanism able to produce sterile neutrinos in the early universe is named Dodelson-Widrow after its inventors, and works thanks to non-zero mixing between active and sterile neutrino species.
Unfortunately, assuming that sterile neutrinos constitute the entire abundance of DM today, this vanilla solution is far from the region of the parameter space in which near future experiments will be sensitive to such particles. Moreover, in the standard scenario it is excluded by X-ray observations.
After introducing the standard scenario and the upcoming experiments involved in the hunt for sterile neutrinos, I will discuss three simple modifications that change drastically the perspectives of detection of this DM candidate in the near future. They have to do with the following questions. What if the universe evolved differently before Big Bang Nucleosynthesis from what is usually assumed? Should we consider the X-ray bound as absolute or model dependent? What if active neutrinos interact among each other also with non-standard interactions?
Dietrich Bödeker