Master Thesis Open Access

Search for $B^+\to K^{*+}\tau^\pm \ell^\mp$ with hadronic tagging at the Belle II experiment

Fuchs, Lara

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    <subfield code="a">&lt;p&gt;Several observables in the flavor sector, including the charged current ratio &lt;span class="math-tex"&gt;\(\mathcal{R}(D^{(*)})\)&lt;/span&gt;&amp;nbsp;and the evidence for neutral current &lt;span class="math-tex"&gt;\(B^+\to K^+\nu\bar\nu\)&lt;/span&gt;&amp;nbsp;have been hinting at deviation from the Standard Model.&lt;br&gt;
Many proposed extensions predict enhanced rates for lepton flavor violating transitions such as &lt;span class="math-tex"&gt;\(b \to s \tau\ell\)&lt;/span&gt;,&amp;nbsp;as there is no fundamental symmetry&amp;nbsp;protecting lepton flavor conservation.&amp;nbsp;&lt;/p&gt;

&lt;p&gt;This thesis provides first estimates of the upper limits on the branching fractions for &lt;span class="math-tex"&gt;\(B^+\to K^{*+}\tau^\pm \ell^\mp\)&lt;/span&gt;&amp;nbsp;decay modes, using simulated samples corresponding to a dataset of &lt;span class="math-tex"&gt;\(365\,\mathrm{fb}^{-1}\)&lt;/span&gt;&amp;nbsp;collected at the&lt;span class="math-tex"&gt;\(\Upsilon (4\mathrm{S})\)&lt;/span&gt;&amp;nbsp;resonance by the Belle II experiment. The accompanying&amp;nbsp;&lt;span class="math-tex"&gt;\(B\)&lt;/span&gt;&amp;nbsp;meson is reconstructed exclusively via hadronic decay modes, enabling&amp;nbsp;signal extraction via a fit to the reconstructed&amp;nbsp;invariant mass of the &lt;span class="math-tex"&gt;\(\tau\)&lt;/span&gt;&amp;nbsp;lepton.&lt;/p&gt;</subfield>
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Publication date:
September 30, 2025
Awarding University:
Karlsruhe Institute of Technology (KIT)
Report Number:
ETP-KA/2025-16
Communities:

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