Détection indirecte de matière noire : des galaxies naines sphéroïdes en photons gamma à la recherche d'anti-hélium avec l'expérience AMS-02

Abstract : Many astrophysical observations suggest the existence of large amounts of missing mass in the Universe, from the galactic to the cosmological scale. Discovering the nature of this invisible mass forms the dark matter problem, which appears as one of the major challenges of modern physics. This thesis is established in the context of indirect detection of dark matter. The latter could consist of new elementary particles, whose annihilation products may be observed in cosmic rays. We study in this work two of the most promising research channels!: gamma-rays and anti-nuclei.The best constraints on dark matter properties from gamma-ray observations come from the dwarf spheroidal galaxies (dSphs) of the Milky Way. The first part of our work was devoted to computing the annihilation J-factors of these objects, which quantify the magnitude of the expected gamma-ray flux. We have developed an optimized Jeans analysis setup in order to reconstruct the dark matter density profiles of these objects and their associated uncertainties, using stellar kinematic data. Our optimized setup was obtained using systematic tests on numerous simulated dSphs, and we applied it to twenty-three dSphs of the Milky Way. The second part of our work was dedicated to the search for anti-helium nuclei in the cosmic ray data collected by the AMS-02 experiment on the International Space Station. We have developed a classification method using boosted decision trees, and our preliminary analysis has led to the best constraints to date on the anti-helium to helium ratio.
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Vincent Bonnivard. Détection indirecte de matière noire : des galaxies naines sphéroïdes en photons gamma à la recherche d'anti-hélium avec l'expérience AMS-02. Astrophysique [astro-ph]. Université Grenoble Alpes, 2016. Français. ⟨NNT : 2016GREAY022⟩. ⟨tel-01485589⟩

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