Abstract
Simple models of weakly interacting massive particles (WIMPs) predict dark matter annihilations into pairs of electroweak gauge bosons, Higgses or tops, which through their subsequent cascade decays produce a spectrum of gamma rays. Intriguingly, an excess in gamma rays coming from near the Galactic center has been consistently observed in Fermi data. A recent analysis by the Fermi collaboration confirms these earlier results. Taking into account the systematic uncertainties in the modelling of the gamma ray backgrounds, we show for the first time that this excess can be well fit by these final states. In particular, for annihilations to (WW, ZZ, hh, tt̄), dark matter with mass between threshold and approximately (165, 190, 280, 310) GeV gives an acceptable fit. The fit range for bb̄ is also enlarged to 35 GeV ≲ mχ ≲ 165 GeV. These are to be compared to previous fits that concluded only much lighter dark matter annihilating into b, τ, and light quark final states could describe the excess. We demonstrate that simple, well-motivated models of WIMP dark matter including a thermal-relic neutralino of the MSSM, Higgs portal models, as well as other simplified models can explain the excess.
Highlights
The weakly interacting massive particle (WIMP) is a well-motivated scenario for dark matter. It explains the observed abundance of dark matter as arising from thermal freeze out of the weakly interacting massive particles (WIMPs) — a particle with a mass and annihilation cross section at the weak scale. This picture suggests that dark matter (DM) particles participate in weak interactions and/or the mechanism for electroweak symmetry breaking
We study the consequence of dark matter annihilations to electroweak bosons and top quarks
We find that WIMP dark matter annihilating to W ’s, Z’s, Higgses, or tops, can fit the observed excess reasonably well
Summary
The weakly interacting massive particle (WIMP) is a well-motivated scenario for dark matter. Their envelope is a good representation of the systematic uncertainties, but does not account for the fit uncertainties. It is interesting to notice the rough similarity between the two panels of Figure 1 This observation leads to the consideration of dark matter models that could explain the GCE with dark matter annihilating to electroweak bosons or to tops. We find that WIMP dark matter annihilating to W ’s, Z’s, Higgses, or tops, can fit the observed excess reasonably well We show that this is the case for the spectra found in [13], and this result is reinforced by the recent Fermi result.
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