A Tentative Gamma-Ray Line from Dark Matter Annihilation at the Fermi Large Area Telescope
The observation of a gamma-ray line in the cosmic-ray ﬂuxes would be a smoking-gun signature for dark matter annihilation or decay in the Universe.
We present an improved search for such signatures in the data of the Fermi Large Area Telescope (LAT), concentrating on energies between 20 and 300 GeV. Besides updating to 43 months of data, we use a new data-driven technique to select optimized target regions depending on the proﬁle of the Galactic dark matter halo. In regions close to the Galactic center, we ﬁnd a 4.6σ indication for a gamma-ray line at Eγ ≈ 130 GeV. When taking into account the look elsewhere eﬀect the signiﬁcance of the observed excess is 3.3σ.
If interpreted in terms of dark matter particles annihilating into a photon pair, the observations imply a dark matter mass of mχ = 129.8 ± 2.4+7−13 GeV and a partial annihilation cross-section of <σvχχ→γγ >=(1.27 ± 0.32+0.18−0.28)×10−27cm3s−1 when using the Einasto dark matter proﬁle.
The evidence for the signal is based on about 50 photons; it will take a few years of additional data to clarify its existence.
Read more: http://arxiv.org/pdf/1204.2797v1.pdf
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