Dark Matter Sees The Light

TL;DR

The paper develops a Unified Dark Matter Module to test annihilating DM explanations of PAMELA and ATIC/PPB-BETS within a broad landscape of models. By computing the injection spectra for $e^+$, $ar{p}$, $\gamma$, and $\nu$ and embedding them in a semi-analytic astrophysical framework, the authors quantify how particle-physics choices (such as a light dark-sector mediator and possible dark-sector shower) and astrophysical uncertainties (halo profiles and propagation) shape the expected signals. They find that while DM explanations generically face tension with high-energy photon data from HESS, carefully chosen parameters (e.g., $m_ ext chi \sim$ TeV, $m_\phi$ in the few hundred MeV range, and modest $\alpha_{\rm DM}$ with a dark-sector shower) can still be compatible; decaying DM and less cuspy profiles can ease the constraints. The work highlights the crucial role of gamma-ray observations, upcoming FERMI/HESS results, and neutrino telescopes in distinguishing among leptophilic DM scenarios and constraining the underlying DM physics. Overall, the study provides a practical framework to map DM models onto multi-messenger indirect-detection data and emphasizes that forthcoming data will be decisive for confirming or ruling out these explanations of the lepton excesses.

Abstract

We construct a Dark Matter (DM) annihilation module that can encompass the predictions from a wide array of models built to explain the recently reported PAMELA and ATIC/PPB-BETS excesses. We present a detailed analysis of the injection spectrums for DM annihilation and quantitatively demonstrate effects that have previously not been included from the particle physics perspective. With this module we demonstrate the parameter space that can account for the aforementioned excesses and be compatible with existing high energy gamma ray and neutrino experiments. However, we find that it is relatively generic to have some tension between the results of the HESS experiment and the ATIC/PPB-BETS experiments within the context of annihilating DM. We discuss ways to alleviate this tension and how upcoming experiments will be able to differentiate amongst the various possible explanations of the purported excesses.

Figures (17)

• Figure 1: An example of $\chi$ annihilation, $\chi\chi\rightarrow\phi\phi\rightarrow e^+e^-e^+e^-$ via the mixing of $\phi$ and $\gamma$.
• Figure 2: An example of $\chi\chi$ annihilation, with the inclusion of the dark sector shower.
• Figure 3: $dN/dx$ for $\bar{p},e^+,\gamma,$ and $\nu$ for the various $m_\phi$ used. The SM contribution from $\chi\chi\rightarrow VV$ is also shown. In the range of $x$ plotted we never reach $\Lambda_{QCD}/m_\chi$ thus the shapes are universal and independent of $m_\chi$, even for the antiprotons.
• Figure 4: Photon and positron spectrum for the two body decay $\chi\chi\rightarrow e^+e^-$ (dashed red line). For comparison, we also plot the four body decay $\chi\chi\rightarrow2\phi\rightarrow 2e^+2e^-$ (solid blue line).
• Figure 5: The effect of varying $\alpha_{\rm DM}$ over the range given in Table \ref{['tab:params']}. We plot $dN/dx$ for a given particle type with a fixed $m_\chi=1$ TeV and various $m_\phi$.