High Energy Positrons and the WMAP Haze from Exciting Dark Matter

TL;DR

This paper explores how exciting dark matter annihilation could produce high-energy positrons and electrons, potentially explaining signals like the WMAP haze, with implications for current and future cosmic ray observations.

Contribution

It introduces a model where light force carriers enable boosted electrons and positrons from dark matter annihilation, linking it to observed astrophysical signals.

Findings

Signals can explain HEAT, PAMELA, and WMAP haze observations.

High dark matter densities are often needed for significant signals.

Positron fraction measurements are robust against halo model variations.

Abstract

We consider the signals of positrons and electrons from "exciting" dark matter (XDM) annihilation. Because of the light (m_phi ~< 1 GeV) force carrier phi into which the dark matter states can annihilate, the electrons and positrons are generally very boosted, yielding a hard spectrum, in addition to the low energy positrons needed for INTEGRAL observations of the galactic center. We consider the relevance of this scenario for HEAT, PAMELA and the WMAP "haze," focusing on light (m_phi ~< 2 m_pi) phi bosons, and find that significant signals can be found for all three, although significant signals generally require high dark matter densities. We find that measurements of the positron fraction are generally insensitive to the halo model, but do suffer significant astrophysical uncertainties. We discuss the implications for upcoming PAMELA results.