The Case for a 700+ GeV WIMP: Cosmic Ray Spectra from PAMELA, Fermi and ATIC

TL;DR

This paper argues that a 700+ GeV WIMP dark matter particle, with Sommerfeld-enhanced annihilation, can explain multiple cosmic ray anomalies observed by PAMELA, Fermi, HESS, and WMAP, predicting detectable gamma-ray signals.

Contribution

It presents a unified dark matter model explaining various cosmic ray excesses and gamma-ray signals, emphasizing leptonic annihilation modes and Sommerfeld enhancement.

Findings

Dark matter annihilation models fit PAMELA, Fermi, HESS, and WMAP data.

Predicted gamma-ray signals from inverse-Compton scattering are detectable.

Models require cross sections consistent with Sommerfeld enhancement.

Abstract

Multiple lines of evidence indicate an anomalous injection of high-energy e+- in the Galactic halo. The recent $e^+$ fraction spectrum from the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) shows a sharp rise up to 100 GeV. The Fermi Gamma-ray Space Telescope has found a significant hardening of the e+e- cosmic ray spectrum above 100 GeV, with a break, confirmed by HESS at around 1 TeV. The Advanced Thin Ionization Calorimeter (ATIC) has also detected detected a similar excess, falling back to the expected spectrum at 1 TeV and above. Excess microwaves towards the galactic center in the WMAP data are consistent with hard synchrotron radiation from a population of 10-100 GeV e+- (the WMAP ``Haze''). We argue that dark matter annihilations can provide a consistent explanation of all of these data, focusing on dominantly leptonic modes, either directly or through a new light boson. Normalizing the signal to the highest energy evidence (Fermi and HESS), we find that similar cross sections provide good fits to PAMELA and the Haze, and that both the required cross section and annihilation modes are achievable in models with Sommerfeld-enhanced annihilation. These models naturally predict significant production of gamma rays in the galactic center via a variety of mechanisms. Most notably, there is a robust inverse-Compton scattered (ICS) gamma-ray signal arising from the energetic electrons and positrons, detectable at Fermi/GLAST energies, which should provide smoking gun evidence for this production.