Dark Matter Signals from Cascade Annihilations

Abstract

A leading interpretation of the electron/positron excesses seen by PAMELA and ATIC is dark matter annihilation in the galactic halo. Depending on the annihilation channel, the electron/positron signal could be accompanied by a galactic gamma ray or neutrino flux, and the non-detection of such fluxes constrains the couplings and halo properties of dark matter. In this paper, we study the interplay of electron data with gamma ray and neutrino constraints in the context of cascade annihilation models, where dark matter annihilates into light degrees of freedom which in turn decay into leptons in one or more steps. Electron and muon cascades give a reasonable fit to the PAMELA and ATIC data. Compared to direct annihilation, cascade annihilations can soften gamma ray constraints from final state radiation by an order of magnitude. However, if dark matter annihilates primarily into muons, the neutrino constraints are robust regardless of the number of cascade decay steps. We also examine the electron data and gamma ray/neutrino constraints on the recently proposed "axion portal" scenario.

36 pages, 11 figures, 7 tables; references added

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Cited by in corpus (11)

• Constraints on Dark Matter annihilations from reionization and heating of the intergalactic gas
• Bounds on Cross-sections and Lifetimes for Dark Matter Annihilation and Decay into Charged Leptons from Gamma-ray Observations of Dwarf Galaxies
• Nonabelian dark matter: models and constraints
• Extragalactic Inverse Compton Light from Dark Matter Annihilation and the Pamela Positron Excess
• Phenomenology of Dark Matter annihilation into a long-lived intermediate state
• PAMELA, DAMA, INTEGRAL and Signatures of Metastable Excited WIMPs
• ATIC, PAMELA, HESS, Fermi and nearby Dark Matter subhalos
• Extended MSSM Neutralinos as the Source of the PAMELA Positron Excess
• PAMELA/ATIC anomaly from the meta-stable extra dark matter component and the leptophilic Yukawa interaction
• Cosmic Ray Positrons from Annihilations into a New, Heavy Lepton
• On discrepancy between ATIC and Fermi data