Sterile neutrino dark matter, neutrino secret self-interactions, and extra radiation

Understand

keV scale sterile neutrinos are excellent warm dark matter candidates.

• In the early Universe, these can be produced from oscillations and scatterings of active neutrinos.
• However, in the absence of any new physics, this mechanism is in severe tension with observations from X-ray searches.
• In this work, we show that secret self-interactions of active neutrinos, mediated by a scalar, can efficiently produce these sterile neutrinos without being ruled out by X-ray observations.