Fermi/LAT observations of dwarf galaxies highly constrain a dark matter interpretation of excess positrons seen in AMS-02, HEAT, and PAMELA
- Michigan Center for Theoretical Physics, University of Michigan – Ann Arbor, 450 Church St., Ann Arbor (United States)
- Nordita (Nordic Institute for Theoretical Physics), KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, Stockholm (Sweden)
It is shown that a Weakly Interacting Massive dark matter Particle (WIMP) interpretation for the positron excess observed in a variety of experiments, HEAT, PAMELA, and AMS-02, is highly constrained by the Fermi/LAT observations of dwarf galaxies. In particular, this paper examines the annihilation channels that best fit the current AMS-02 data (Boudaud et al., 2014), specifically focusing on channels and parameter space not previously explored by the Fermi/LAT collaboration. The Fermi satellite has surveyed the γ-ray sky, and its observations of dwarf satellites are used to place strong bounds on the annihilation of WIMPs into a variety of channels. For the single channel case, we find that dark matter annihilation into (b b-bar ,e{sup +}e{sup -}, μ{sup +}μ{sup -}, τ{sup +}τ{sup -},4-e or 4-τ ) is ruled out as an explanation of the AMS positron excess (here b quarks are a proxy for all quarks, gauge and Higgs bosons). In addition, we find that the Fermi/LAT 2σ upper limits, assuming the best-fit AMS-02 branching ratios, exclude multichannel combinations into b b-bar and leptons. The tension between the results might relax if the branching ratios are allowed to deviate from their best-fit values, though a substantial change would be required. Of all the channels we considered, the only viable channel that survives the Fermi/LAT constraint and produces a good fit to the AMS-02 data is annihilation (via a mediator) to 4-μ, or mainly to 4-μ in the case of multichannel combinations.
- OSTI ID:
- 22524936
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Vol. 2016, Issue 03; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
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