7 keV Dark Matter as X-ray Line Signal in Radiative Neutrino Model

Understand

We study a light dark matter in a radiative neutrino model to explain the X-ray line signal at about $3.5$ keV recently reported by XMN-Newton X-ray observatory using data of various galaxy clusters and Andromeda galaxy.

• The signal requires very tiny mixing between the dark matter and an active neutrino; $\sin^2 2\theta\approx 10^{-10}$.
• It could suggest that such a light dark matter cannot contribute to the observed neutrino masses if we use the seesaw mechanism.
• In other words, neutrino masses might come a structure different from the dark matter.