Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Kaluza-Klein Dark Matter, Electrons and Gamma Ray Telescopes

Edward A. Baltz, Dan Hooper

TL;DR

This work proposes that Kaluza-Klein dark matter (KKDM) annihilations produce direct $e^+e^-$ pairs, creating a sharp spectral edge at $E \approx m_{\rm KKDM}$ in the high-energy electron–positron flux. By modeling the injection, propagation via the diffusion-loss equation, and realistic Galactic halo assumptions (including a boost factor), the authors quantify the expected edge and assess detectability with gamma-ray telescopes: ground-based Atmospheric Cherenkov Telescopes (ACTs) and the GLAST satellite. They demonstrate that, for KKDM masses up to roughly 600 GeV, high-significance detections of the edge are achievable with multi-year observations, given plausible experimental specifications and background rejection. The study provides a concrete indirect detection channel for KKDM and maps the required instrument performance (energy resolution, hadron rejection, and exposure) to realize this signature in current or upcoming experiments.

Abstract

Kaluza-Klein dark matter particles can annihilate efficiently into electron-positron pairs, providing a discrete feature (a sharp edge) in the cosmic $e^+ e^-$ spectrum at an energy equal to the particle's mass (typically several hundred GeV to one TeV). Although this feature is probably beyond the reach of satellite or balloon-based cosmic ray experiments (those that distinguish the charge and mass of the primary particle), gamma ray telescopes may provide an alternative detection method. Designed to observe very high-energy gamma-rays, ACTs also observe the diffuse flux of electron-induced electromagnetic showers. The GLAST satellite, designed for gamma ray astronomy, will also observe any high energy showers (several hundred GeV and above) in its calorimeter. We show that high-significance detections of an electron-positron feature from Kaluza-Klein dark matter annihilations are possible with GLAST, and also with ACTs such as HESS, VERITAS or MAGIC.

Kaluza-Klein Dark Matter, Electrons and Gamma Ray Telescopes

TL;DR

This work proposes that Kaluza-Klein dark matter (KKDM) annihilations produce direct pairs, creating a sharp spectral edge at in the high-energy electron–positron flux. By modeling the injection, propagation via the diffusion-loss equation, and realistic Galactic halo assumptions (including a boost factor), the authors quantify the expected edge and assess detectability with gamma-ray telescopes: ground-based Atmospheric Cherenkov Telescopes (ACTs) and the GLAST satellite. They demonstrate that, for KKDM masses up to roughly 600 GeV, high-significance detections of the edge are achievable with multi-year observations, given plausible experimental specifications and background rejection. The study provides a concrete indirect detection channel for KKDM and maps the required instrument performance (energy resolution, hadron rejection, and exposure) to realize this signature in current or upcoming experiments.

Abstract

Kaluza-Klein dark matter particles can annihilate efficiently into electron-positron pairs, providing a discrete feature (a sharp edge) in the cosmic spectrum at an energy equal to the particle's mass (typically several hundred GeV to one TeV). Although this feature is probably beyond the reach of satellite or balloon-based cosmic ray experiments (those that distinguish the charge and mass of the primary particle), gamma ray telescopes may provide an alternative detection method. Designed to observe very high-energy gamma-rays, ACTs also observe the diffuse flux of electron-induced electromagnetic showers. The GLAST satellite, designed for gamma ray astronomy, will also observe any high energy showers (several hundred GeV and above) in its calorimeter. We show that high-significance detections of an electron-positron feature from Kaluza-Klein dark matter annihilations are possible with GLAST, and also with ACTs such as HESS, VERITAS or MAGIC.

Paper Structure

This paper contains 4 sections, 4 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Electrons and Positrons From Kaluza-Klein Dark Matter
  3. Prospects for Gamma Ray Telescopes
  4. Conclusions

Figures (2)

  • Figure 1: The spectrum of electrons plus positrons, including the effects of propagation, from Kaluza-Klein Dark Matter (KKDM) annihilations. Annihilations of KKDM produce equal fractions of $\tau^+ \tau^-$, $\mu^+ \mu^-$ and $e^+ e^-$ pairs (approximately $20\%$ each) as well as up-type quarks (approximately $11\%$ per generation), neutrinos (approximately $1.2\%$ per generation), Higgs bosons (approximately $2.3\%$) and down-type quarks (approximately $0.7\%$ per generation). Results for KKDM with masses of 300 and 600 GeV are shown. An NFW dark matter distribution with a boost factor of 5 and $\rho_{\rm{local}}=0.4 \,\rm{GeV/cm^3}$ was used.
  • Figure 2: The significance of the $e^{\pm}$ feature from Kaluza-Klein dark matter annihilations at $E=m_{\rm{KKDM}}$ in a modern Atmospheric Cerenkov Telescope (ACT), such as HESS, VERITAS or MAGIC, as a function of time observed. We have considered an ACT with $15\%$ energy resolution, $99\%$ hadronic rejection, a 0.003 sr field-of-view and $2\times 10^5$ square meters effective area. Results for dark matter masses of 300, 400, 500, 600 and 700 GeV are shown. An NFW dark matter distribution with a boost factor of 5 and $\rho_{\rm{local}}=0.4 \,\rm{GeV/cm^3}$ was used. To compare with GLAST, the exposure time axis should be multiplied by a factor of 16, thus the 600 GeV particle detected at 5$\sigma$ in 3000 hours with an ACT requires 48,000 hours with GLAST. Both datasets could be collected in roughly 7 years.