Pico-charged particles explaining 511 keV line and XENON1T signal

Understand

There is a robust signal for a 511 keV photon line from the galactic center which may originate from dark matter particles with masses of a few MeV.

• To avoid the bounds from delayed recombination and from the absence of the line from dwarf galaxies, in 2017, we have proposed a model in which dark matter first decays into a pair of intermediate pico-charged particles $C\bar{C}$ with a lifetime much larger than the age of the universe.
• The galactic magnetic field accumulates the relativistic $C\bar{C}$ that eventually annihilate, producing the $e^-e^+$ pair that give rise to the 511 keV line.
• The relativistic pico-charged $C$ particles can scatter on the electrons inside the direct dark matter search detectors imparting a recoil energy of $E_r \sim$~keV.