511 keV $\gamma$-ray emission from the galactic bulge by MeV millicharged dark matter

TL;DR

This paper proposes that a light, millicharged fermion could explain the 511 keV gamma-ray emission from the galactic bulge by producing positrons, with constraints on its parameters derived from observations.

Contribution

It introduces a novel millicharged fermion model to explain the galactic 511 keV line and constrains its parameters based on cosmic gamma-ray data.

Findings

Constraints on millicharged particle parameters from gamma-ray observations

Potential explanation for the galactic 511 keV emission

No collider detection due to tiny electromagnetic charge

Abstract

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