Dark Matter Annihilation from Nearby Ultra-compact Micro Halos to Explain the Tentative Excess at ~1.4 TeV in DAMPE data

TL;DR

This paper investigates whether ultra-compact micro halos (UCMHs) near Earth could explain the 1.4 TeV excess in DAMPE's electron-positron spectrum through dark matter annihilation.

Contribution

It demonstrates that UCMHs with typical parameters can account for the DAMPE excess without conflicting with existing cosmological constraints.

Findings

UCMHs can produce enough electrons and positrons to explain the DAMPE excess.

The required fraction of dark matter in UCMHs is as low as 10^-5.

UCMHs are consistent with current cosmological and astrophysical limits.

Abstract

The tentative 1.4 TeV excess in the $e^+e^-$ spectrum measured by The DArk Matter Particle Explorer (DAMPE) motivates the possible existence of one or more local dark matter concentrated regions. In particular, Ultra-compact Micro Halos (UCMHs) seeded by large density perturbations in the early universe, allocated within ~0.3 kpc from the solar system, could provide the potential source of electrons and positrons produced from dark matter annihilation, enough to explain the DAMPE signal. Here we consider a UCMH with density profile assuming radial in-fall and explore the preferred halo parameters to explain the 1.4 TeV "DAMPE excess". We find that typical parameter space of UCMHs can easily explain the "DAMPE excess" with usual thermal-averaged annihilation cross section of WIMP. The fraction of dark matter stored in such UCMHs in the Galactic-scale halo can be reduced to as small as $O(10^{-5})$, well within the current cosmological and astrophysical constraints.