Abstract
We present the results of stereoscopic observations of the satellite galaxy Segue 1 with the MAGIC Telescopes, carried out between 2011 and 2013. With almost 160 hours of good-quality data, this is the deepest observational campaign on any dwarf galaxy performed so far in the very high energy range of the electromagnetic spectrum. We search this large data sample for signals of dark matter particles in the mass range between 100 GeV and 20 TeV. For this we use the full likelihood analysis method, which provides optimal sensitivity to characteristic gamma-ray spectral features, like those expected from dark matter annihilation or decay. In particular, we focus our search on gamma-rays produced from different final state Standard Model particles, annihilation with internal bremsstrahlung, monochromatic lines and box-shaped signals. Our results represent the most stringent constraints to the annihilation cross-section or decay lifetime obtained from observations of satellite galaxies, for masses above few hundred GeV. In particular, our strongest limit (95% confidence level) corresponds to a ∼ 500 GeV dark matter particle annihilating into τ+τ−, and is of order ⟨σannv⟩ ≃ 1.2 × 10−24 cm3 s−1 — a factor ∼ 40 above the ⟨σannv⟩ ≃ thermal value.
Highlights
The search for WIMPs is conducted on three complementing fronts, namely: production in particle accelerators, direct detection in underground experiments and indirect detection
There are two aspects of the full likelihood analysis applied in this work that carry advantages for DM searches with Imaging Air Cherenkov Telescopes (IACTs): i) a sensitivity improvement due to the use of specific spectral signatures — such as those coming from DM annihilation and decay, and, ii) the combination of results from different data samples, e.g. obtained under different experimental conditions, becomes a trivial operation
Results from line searches when DM particles annihilate into a photon and a Z boson are shown in figure 16: the strongest bound from this work corresponds to σannv ∼ 7.8×10−26 cm3 s−1, for mχ ∼ 250 GeV
Summary
The search for WIMPs is conducted on three complementing fronts, namely: production in particle accelerators, direct detection in underground experiments and indirect detection. The current status of these experimental searches strengthens the motivation for DM particles with masses at the TeV scale or above — the mass range best (and sometimes exclusively) covered by the Imaging Air Cherenkov Telescopes (IACTs) For this reason, IACT observations in the very high energy domain (E 100 GeV) provide extremely valuable clues to unravel the nature of the DM. We improve our previous limits, obtained from ∼30 hours of Segue 1 observations in the single telescope mode [19], by one order of magnitude This improvement is achieved through the increased sensitivity of the MAGIC stereo system, the deep exposure, and the use of the full likelihood analysis [28] — a method optimized for searches of characteristic, DM-induced gamma-ray spectral features.
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