keV photon emission from light nonthermal dark matter
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We propose a possible explanation for the recent claim of an excess at 3.5 keV in the x-ray spectrum within a minimal extension of the standard model that explains dark matter and baryon abundance of the Universe. The dark matter mass in this model is O(GeV) and its relic density has a nonthermal origin. The model includes two colored scalars of O(TeV) mass (X1,2), and two singlet fermions that are almost degenerate in mass with the proton (N1,2). The heavier fermion N2 undergoes radiative decay to the lighter one N1 that is absolutely stable. Radiative decay with a lifetime 1023 seconds can account for the claimed 3.5 keV line, which requires couplings 10-3-10-1 between X1,2, N1,2 and the up-type quarks. The model also gives rise to potentially detectable monojet, dijet, and monotop signals at the LHC. 2014 American Physical Society.