Charge Asymmetric Cosmic Ray Signals From Dark Matter Decay

Abstract

The PAMELA and Fermi measurements of the cosmic-ray electron and positron spectra have generated much interest over the past two years, because they are consistent with a significant component of the electron and positron fluxes between 20 GeV and 1 TeV being produced through dark matter annihilation or decay. However, since the measurements are also consistent with astrophysical interpretations, the message is unclear. In this paper, we point out that dark matter can have a more distinct signal in cosmic rays, that of a charge asymmetry. Such charge asymmetry can result if the dark matter's abundance is due to a relic asymmetry, allowing its decay to generate an asymmetry in positrons and electrons. This is analogous to the baryon asymmetry, where decaying neutrons produce electrons and not positrons. We explore benchmark scenarios where the dark matter decays into a leptophilic charged Higgs boson or electroweak gauge bosons. These models have observable signals in gamma rays and neutrinos, which can be tested by Fermi and IceCube. The most powerful test will be at AMS-02, given its ability to distinguish electron and positron charge above 100 GeV. Specifically, an asymmetry favoring positrons typically predicts a larger positron ratio and a harder (softer) high energy spectrum for positrons (electrons) than charge symmetric sources. We end with a brief discussion on how such scenarios differ from the leading astrophysical explanations.

8 pages, 11 figures, revtex; v2, additional references added

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Cited by in corpus (26)

• Review of asymmetric dark matter
• Dark Matter and Pulsar Origins of the Rising Cosmic Ray Positron Fraction in Light of New Data From AMS
• HAWC Observations Strongly Favor Pulsar Interpretations of the Cosmic-Ray Positron Excess
• Lessons from HAWC PWNe observations: the diffusion constant is not a constant; Pulsars remain the likeliest sources of the anomalous positron fraction; Cosmic rays are trapped for long periods of time in pockets of inefficient diffusion
• Regenerating a Symmetry in Asymmetric Dark Matter
• Implications of the first AMS-02 measurement for dark matter annihilation and decay
• Constraining the origin of the rising cosmic ray positron fraction with the boron-to-carbon ratio
• Cosmic Coincidence and Asymmetric Dark Matter in a Stueckelberg Extension
• Dynamical Dark Matter and the Positron Excess in Light of AMS
• Measuring the Local Diffusion Coefficient with H.E.S.S. Observations of Very High-Energy Electrons
• Possible Evidence for the Stochastic Acceleration of Secondary Antiprotons by Supernova Remnants
• New Constraints from PAMELA anti-proton data on Annihilating and Decaying Dark Matter
• Eight-channel reconfigurable microring filters with tunable frequency, extinction ratio and bandwidth
• Decaying Asymmetric Dark Matter Relaxes the AMS-Fermi Tension
• Features in the Spectrum of Cosmic-Ray Positrons from Pulsars
• Utilizing cosmic-ray positron and electron observations to probe the averaged properties of Milky Way pulsars
• Snowmass-2013 Cosmic Frontier 3 (CF3) Working Group Summary: Non-WIMP dark matter
• Charge Asymmetric Cosmic Rays as a probe of Flavor Violating Asymmetric Dark Matter
• Cosmic Ray-Dark Matter Scattering: a New Signature of (Asymmetric) Dark Matter in the Gamma Ray Sky
• Baryogenesis via Leptogenesis from Asymmetric Dark Matter and radiatively generated Neutrino mass
• Gamma Ray Constraints on Flavor Violating Asymmetric Dark Matter
• Hints of a Charge Asymmetry in the Electron and Positron Cosmic-Ray Excesses
• Revisiting GeV-scale annihilating dark matter with the AMS-02 positron fraction
• Observing Signals of Spectral Features in the Cosmic-Ray Positrons and Electrons from Milky Way Pulsars
• On the scattering of a high-energy cosmic ray electrons off the dark matter
• Possible counterpart signal of the Fermi bubbles at the cosmic-ray positrons