A Dynamical Framework for KeV Dirac Neutrino Warm Dark Matter

Understand

If the source of the reported $3.5$ keV x-ray line is a sterile neutrino, comprising an $\mathcal{O}(1)$ fraction of the dark matter (DM), then it exhibits the property that its mass times mixing angle is $\sim \mbox{few} \times 10^{-2}$ eV, a plausible mass scale for the active neutrinos.

• This property is a common feature of Dirac neutrino mixing.
• We present a framework that dynamically produces light active and keV sterile Dirac neutrinos, with appropriate mixing angles to be the x-ray line source.
• The central idea is that the right-handed active neutrino is a composite state, while elementary sterile neutrinos gain keV masses similarly to the quarks in extended Technicolor.