Pico-charged particles from dark matter decay explain the 511 keV line and the XENON1T signal

Y Farzan,M Rajaee

doi:10.1103/physrevd.102.103532

Y Farzan, M Rajaee

Open Access

https://doi.org/10.1103/physrevd.102.103532

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Abstract

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 the 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 $C\overline{C}$ with a lifetime much larger than the age of the Universe. The Galactic magnetic field accumulates the relativistic $C\overline{C}$ that eventually annihilate, producing the ${e}^{\ensuremath{-}}{e}^{+}$ pair that gives 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 ${E}_{r}\ensuremath{\sim}\mathrm{keV}$. We show that this model can account for the electron recoil excess recently reported by the XENON1T experiment. Moreover, we show that the XENON1T electron recoil data set the most stringent bound on the lifetime of the dark matter within this model.

Highlights

From the cosmological scales down to the galactic scales, dark matter has demonstrated its existence via gravitational effects
No conclusive discovery has so far been made, various observations have been reported that defy an explanation within the standard model and may have a dark matter origin
We show that our model can simultaneously explain the 511 keV line and the XENON1T excess

Summary

INTRODUCTION

From the cosmological scales down to the galactic scales, dark matter has demonstrated its existence via gravitational effects. One of them is the observation of the 511 keV line from the Galactic Center Another signal is the recently reported XENON1T electron recoil signal [1]. The XENON1T detector has reported an excess of scattered electrons with recoil energies 1–7 keV over the background. Despite their small mass, the scattering of the C particles off the electrons can impart a sizable recoil energy In this model, the interaction of the C particles with the electrons (as well as with the protons) takes place via the t-channel virtual SM photon (i.e., via Coulomb interaction) and dark photon exchanges.

THE MODEL

BOUNDS ON THE PARAMETERS

PREDICTIONS FOR DIRECT DARK MATTER SEARCH EXPERIMENTS

E2r where

10 MeV mX

SUMMARY AND CONCLUSIONS