511 keV γ-ray emission from the galactic bulge by MeV millicharged dark matter

We propose a possible explanation for the recently observed anomalous 511 keV tine with a new "millicharged" fermion. The new fermion is light [O(MeV)]. Nevertheless, it has never been observed by any collider experiments by virtue of its tiny electromagnetic charge se. In particular, we constrain parameters of thus millicharged particle if the 511 keV cosmic gamma-ray emission from the galactic bulge is due to positron production from thus new particle.