Master Thesis Open Access

Sensitivity Study in the Search for $B^{\pm}\to K^{\pm}a$ (displaced $a\to\gamma\gamma$) Decays at Belle II

Heidelbach, Alexander

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  <dc:creator>Heidelbach, Alexander</dc:creator>
  <dc:date>2022-04-28</dc:date>
  <dc:description>In a set of simple extensions of the Standard Model, Axion Like Particles (ALPs) arise as pseudo Nambu-Goldstone bosons of theories with a spontaneously broken Peccei-Quinn symmetry that is anomalous under the Standard Model gauge symmetry. Due to constraints in flavour-changing current  (FCNC) processes, involving the coupling of ALPs directly to Standard Model fermions and gluons, direct couplings of ALPs to the electroweak gauge bosons are particularly interesting. As a result of a coupling to $W$ bosons, ALPs can emerge in FCNC $b\to s$ transitions. Depending on the ALP mass and the coupling strength to photons a possible experimental signature is $B^{\pm}\to K^{\pm}a, a\to\gamma\gamma$ with long lived ALP decays. This thesis performs a sensitivity study in the search for the $B^{\pm}\to K^{\pm}a, a\to\gamma\gamma$ signature based on Belle II simulation samples corresponding to an integrated luminosity of 100\,fb$^{-1}$. The sensitivity study includes an optimised candidate selection and signal yield scans of the invariant di-photon mass distribution in the range of $0.175\,\text{GeV/c}^2$ to $4.600\,\text{GeV/c}^2$ for eight different ALP lifetimes between $0\,\text{cm}$ and $50\,\text{cm}$. Resulting expected limits are comparable to a similar search for $B^{\pm}\to K^{\pm}a, a\to\gamma\gamma$ on data collected by the BABAR experiment. </dc:description>
  <dc:identifier>https://publish.etp.kit.edu/record/22123</dc:identifier>
  <dc:identifier>oai:publish.etp.kit.edu:22123</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:subject>Belle II</dc:subject>
  <dc:subject>Analysis</dc:subject>
  <dc:subject>Search for New Physics</dc:subject>
  <dc:subject>ALPs</dc:subject>
  <dc:title>Sensitivity Study in the Search for $B^{\pm}\to K^{\pm}a$ (displaced $a\to\gamma\gamma$) Decays 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:
April 28, 2022
Keyword(s):
Belle II Analysis Search for New Physics ALPs
Awarding University:
Karlsruhe Institute of Technology (KIT)
Report Number:
ETP-KA/2022-03
Communities:

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