On the Dark Matter Solutions to the Cosmic Ray Lepton Puzzle

TL;DR

This paper critically examines the hypothesis that dark matter annihilations explain cosmic ray lepton excesses, finding that natural models are insufficient and that alternative explanations are more plausible.

Contribution

It provides a thorough review and constraints on dark matter models as explanations for cosmic ray lepton excesses, challenging their naturalness and likelihood.

Findings

Dark matter models require unnatural signal enhancements.

PAMELA antiproton data constrains dark matter contributions.

Nearby dark matter clumps are unlikely sources based on simulations.

Abstract

Recent measurements of cosmic ray leptons by PAMELA, ATIC, HESS and Fermi revealed interesting excesses. Many authors suggested particle Dark Matter (DM) annihilations could be at the origin of these effects. In this paper, we critically assess this interpretation by reviewing some results questioning the naturalness and robustness of such an interpretation. Natural values for the DM particle parameters lead to a poor leptons production so that models often require signal enhancement effects that we constrain here. Considering DM annihilations are likely to produce antiprotons as well, we use the PAMELA antiproton to proton ratio measurements to constrain a possible exotic contribution. We also consider the possibility of an enhancement due to a nearby clump of DM. This scenario appears unlikely when compared to the state-of-the-art cosmological N-body simulations. We conclude that the bulk of the observed signals most likely has no link with DM and is rather a new, yet unconsidered source of background for searches in these channels.