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Register a new userGamma-ray Constraints on Decaying Dark Matter and Implications for IceCube
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Utilizing the Fermi measurement of the gamma-ray spectrum toward the Galactic Center, we derive some of the strongest constraints to date on the dark matter (DM) lifetime in the mass range from hundreds of MeV to above an EeV. Our profile-likelihood based analysis relies on 413 weeks of Fermi Pass 8 data from 200 MeV to 2 TeV, along with up-to-date models for diffuse gamma-ray emission within the Milky Way. We model Galactic and extragalactic DM decay and include contributions to the DM-induced gamma-ray flux resulting from both primary emission and inverse-Compton scattering of primary electrons and positrons. For the extragalactic flux, we also calculate the spectrum associated with cascades of high-energy gamma-rays scattering off of the cosmic background radiation. We argue that a decaying DM interpretation for the 10 TeV-1 PeV neutrino flux observed by IceCube is disfavored by our constraints. Our results also challenge a decaying DM explanation of the AMS-02 positron flux. We interpret the results in terms of individual final states and in the context of simplified scenarios such as a hidden-sector glueball model.
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Among the several strategies for indirect searches of dark matter, one very promising one is to look for the gamma-rays from decaying dark matter. Here we use the most up-to-date upper bounds on the gamma-ray flux from $10^5$ to $10^{11}$ GeV, obtained from CASA-MIA, KASCADE, KASCADE-Grande, Pierre Auger Observatory, and Telescope Array. We obtain global limits on dark matter lifetime in the range of masses $m_mathrm{DM}=[10^7-10^{15}]~mathrm{GeV}$. We provide the bounds for a set of decay channels chosen as representatives. The constraints derived here are new and cover a region of the parameter space not yet explored. We compare our results with the projected constraints from future neutrino telescopes, in order to quantify the improvement that will be obtained by the complementary high-energy neutrino searches.
If the dark matter is unstable, the decay of these particles throughout the universe and in the halo of the Milky Way could contribute significantly to the isotropic gamma-ray background (IGRB) as measured by Fermi. In this article, we calculate the high-latitude gamma-ray flux resulting from dark matter decay for a wide range of channels and masses, including all contributions from inverse Compton scattering and accounting for the production and full evolution of cosmological electromagnetic cascades. We also make use of recent multi-wavelength analyses that constrain the astrophysical contributions to the IGRB, enabling us to more strongly restrict the presence any component arising from decaying dark matter. Over a wide range of decay channels and masses (from GeV to EeV and above), we derive stringent lower limits on the dark matters lifetime, generally in the range of $tau sim (1-5)times 10^{28}$ s.
New bounds on decaying Dark Matter are derived from the gamma-ray measurements of (i) the isotropic residual (extragalactic) background by Fermi and (ii) the Fornax galaxy cluster by H.E.S.S. We find that those from (i) are among the most stringent constraints currently available, for a large range of dark matter masses and a variety of decay modes, excluding half-lives up to about 10^26 to few 10^27 seconds. In particular, they rule out the interpretation in terms of decaying dark matter of the e+/- spectral features in PAMELA, Fermi and H.E.S.S., unless very conservative choices are adopted. We also discuss future prospects for CTA bounds from Fornax which, contrary to the present H.E.S.S. constraints of (ii), may allow for an interesting improvement and may become better than those from the current or future extragalactic Fermi data.
We derive 95% CL lower limits on the lifetime of decaying dark matter in the channels $Z u$, $Well$ and $h u$ using measurements of the cosmic-ray antiproton flux by the PAMELA experiment. Performing a scan over the allowed range of cosmic-ray propagation parameters we find lifetime limits in the range of $8 times 10^{28}$s to $5 times 10^{25}$s for dark matter masses from roughly 100 GeV to 10 TeV. We apply these limits to the well-motivated case of gravitino dark matter in scenarios with bilinear violation of R-parity and find a similar range of lifetime limits for the same range of gravitino masses. Converting the lifetime limits to constraints on the size of the R-parity violating coupling we find upper limits in the range of $10^{-8}$ to $8 times 10^{-13}$.
We report on constraints on the lifetime of decaying gravitino dark matter in models with bilinear R-parity violation derived from observations of cosmic-ray antiprotons with the PAMELA experiment. Performing a scan over a viable set of cosmic-ray propagation parameters we find lower limits ranging from $8times 10^{28}$s to $6times 10^{28}$s for gravitino masses from roughly 100 GeV to 10 TeV. Comparing these limits to constraints derived from gamma-ray and neutrino observations we conclude that the presented antiproton limits are currently the strongest and most robust limits on the gravitino lifetime in the considered mass range. These constraints correspond to upper limits on the size of the bilinear R-parity breaking parameter in the range of $10^{-8}$ to $8times 10^{-13}$.
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