Thesis defense of Stefan Fröse

Despite its elusive nature, dark matter is suspected of shaping the universe as we know it today. Over the past decades, various theories for its properties have emerged, most of them allowing for a coupling of the dark sector to the standard model. Dark matter candidates, such as Weakly Interacting Massive Particles (WIMPs), can annihilate to standard model particles, leading to the subsequent production of photons, whose direct production is otherwise suppressed. A substantial rate of gamma rays is expected to emerge in regions with high dark matter density, such as dwarf galaxies.
This thesis studies gamma-ray signals that are expected from CBe dSph with the MAGIC telescopes in both energy and spatial dimensions. Since the telescopes detect extensive air showers produced by the interaction of the gamma rays with Earth’s atmosphere, the high rate of cosmic rays dominates the background of these observations. The impurity of signal-background separation methods necessitates the construction of a three-dimensional background model for this analysis, leading to the proposal of a novel modeling approach, the exclusion-rotation method.
Preceding studies relied on the one-dimensional, energy-only analysis of CBe dSph. By incorporating two additional dimensions in this work, the computational construction of upper limits on the thermal-averaged cross-section of the dark matter models demands a robust and efficient calculation of statistical tests. Asimov datasets are introduced and applied for the first time in the context of a dark matter search using the MAGIC telescopes. These datasets enable the approximation of the test statistics, allowing for the first-ever construction of upper limits on the strength modifier of the dark matter model with the CLs method. The implementation of these novel methods in this work is provided through the open-source Python package TITRATE.
No evidence of a dark matter-induced signal for annihilation to bb‾, W+W-, μ+μ-, and τ+τ- and dark matter masses mχ between 0.17 TeV and 100 TeV in CBe dSph is found. The performance of the upper limits on the thermal-averaged cross-section calculated with the Asimov datasets in one and three dimensions is compared to the classical construction with Wilks’ theorem. The three-dimensional Asimov CLs sensitivity outperforms preceding studies of CBe dSph by the MAGIC collaboration when scaled to the appropriate dark matter density assumed by MAGIC except for annihilation to τ+τ- for mχ>30TeV.