Master Thesis Open Access

Search for Axion-Like Particles in $e^+ e^- \to e^+ e^- \gamma \gamma$ Events at Belle~II

Schmitt, Frederik


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        "name": "Schmitt, Frederik"
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    "description": "<p>Axion-like particles (ALPs), as analyzed in this thesis, present compelling beyond standard model scenarios with a yet mostly unexplored range in phase space, particularly the GeV ALP-mass range.<br>\nDue to the high collision rate and the high precision detector, the Belle II experiment is an ideal environment to search for GeV ALPs at a particle collider experiment.<br>\nWhile the ALP can decay into multiple signatures, this work focuses on a model where it decays predominantly into two resolved photons.<br>\nExperimentally, this allows the search for a peak in the invariant diphoton mass $M_{\\gamma\\gamma}$ from an ALP decay signal over the SM background.<br>\nBelle~II already published a search for the same ALP model; however, this is the first effort to perform an experimental sensitivity study for the $t$-channel $e^+ e^- \\to e^+ e^- a, a \\to \\gamma \\gamma $ process.<br>\nIn this work, I present an analysis strategy that demonstrates the feasibility of analyzing the fully reconstructed Photon fusion process at Belle II and yields comparable sensitivity to that obtained from analyzing ALP-Strahlung ($\\e^+ e^- \\to \\gamma a, a \\ to \\gamma \\gamma$ events.</p>", 
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      "report_number": "ETP-KA/2025-11", 
      "supervisors": [
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          "affiliation": "KIT/ETP", 
          "name": "Ferber, Torben"
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        {
          "affiliation": "KIT/ETP", 
          "name": "Klute, Markus"
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        {
          "affiliation": "KIT/ETP", 
          "name": "Heidelbach, Alexander"
        }, 
        {
          "affiliation": "KIT/ETP", 
          "name": "De Pietro, Giacomo"
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      ]
    }, 
    "title": "Search for Axion-Like Particles in $e^+ e^- \\to e^+ e^- \\gamma \\gamma$ Events at Belle~II"
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