Dark Matter Interpretations of the Electron/Positron Excesses after FERMI

TL;DR

This paper explores dark matter models as explanations for cosmic-ray positron and electron excesses, analyzing their compatibility with observational constraints and predicting gamma-ray signatures detectable by FERMI.

Contribution

It provides a comprehensive analysis of dark matter annihilation and decay scenarios fitting cosmic-ray excesses, considering constraints and potential gamma-ray signals.

Findings

Tau and 4mu final states fit the excess best

Electron final states are less constrained but require hidden sector radiation

Dark matter below 1 TeV cannot explain the excesses

Abstract

The cosmic-ray excess observed by PAMELA in the positron fraction and by FERMI and HESS in the electron + positron flux can be interpreted in terms of DM annihilations or decays into leptonic final states. Final states into tau's or 4mu give the best fit to the excess. However, in the annihilation scenario, they are incompatible with photon and neutrino constraints, unless DM has a quasi-constant density profile. Final states involving electrons are less constrained but poorly fit the excess, unless hidden sector radiation makes their energy spectrum smoother, allowing a fit to all the data with a combination of leptonic modes. In general, DM lighter than about a TeV cannot fit the excesses, so PAMELA should find a greater positron fraction at higher energies. The DM interpretation can be tested by FERMI gamma observations above 10 GeV: if the electronic excess is everywhere in the DM halo, inverse Compton scattering on ambient light produces a well-predicted gamma excess that FERMI should soon detect.