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Bounds on dark matter interpretation of Fermi-LAT GeV excess

Abstract

Annihilation of light dark matter of mDM(1040)m_{\rm DM} \approx (10-40) GeV into the Standard Model fermions has been suggested as a possible origin of the gamma-ray excess at GeV energies in the Fermi-LAT data. In this paper, we examine possible model-independent signatures of such dark matter models in other experiments such as AMS-02, colliders, and cosmic microwave background (CMB) measurements. We point out that first generation of fermion final states is disfavored by the existing experimental data. Currently AMS-02 positron measurements provide stringent bounds on cross sections of dark matter annihilation into leptonic final states, and e+ee^+e^- final state is in severe tension with this constraint, if not ruled out. The e+ee^+e^- channel will be complementarily verified in an early stage of ILC and future CMB measurements. Light quark final states (qqˉq\bar q) are relatively strongly constrained by the LHC and dark matter direct detection experiments even though these bounds are model-dependent. Dark matter signals from annihilations into qqˉq\bar{q} channels would be constrained by AMS-02 antiproton data which will be released in very near future. In optimistic case, diffuse radio emission from nearby galaxy (clusters) and the galactic center might provide another hint or limit on dark matter annihilation.Comment: 20 pages, 3 figures; figures and text updated, discussion improved, references added; updated to match published version in NP

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