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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  <dc:creator>Schmitt, Frederik</dc:creator>
  <dc:date>2026-01-23</dc:date>
  <dc:description>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.
Due 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.
While the ALP can decay into multiple signatures, this work focuses on a model where it decays predominantly into two resolved photons.
Experimentally, this allows the search for a peak in the invariant diphoton mass $M_{\gamma\gamma}$ from an ALP decay signal over the SM background.
Belle~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.
In 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.</dc:description>
  <dc:identifier>https://publish.etp.kit.edu/record/22389</dc:identifier>
  <dc:identifier>oai:publish.etp.kit.edu:22389</dc:identifier>
  <dc:language>eng</dc:language>
  <dc:relation>url:https://publish.etp.kit.edu/communities/belle2</dc:relation>
  <dc:relation>url:https://publish.etp.kit.edu/communities/etp</dc:relation>
  <dc:rights>info:eu-repo/semantics/openAccess</dc:rights>
  <dc:title>Search for Axion-Like Particles in $e^+ e^- \to e^+ e^- \gamma \gamma$ Events at Belle~II</dc:title>
  <dc:type>info:eu-repo/semantics/masterThesis</dc:type>
  <dc:type>thesis-master-thesis</dc:type>
</oai_dc:dc>
Publication date:
January 23, 2026
Awarding University:
Karlsruhe Institute of Technology (KIT)
Report Number:
ETP-KA/2025-11
Communities:

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