July 22, 2024 Bachelor Thesis Open Access

Bogner, Lars

MARC21 XML Export

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    <subfield code="a">FCC-ee</subfield>
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    <subfield code="a">machine learning</subfield>
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    <subfield code="a">explicit reconstruction</subfield>
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    <subfield code="a">&lt;p&gt;The next generation of e&lt;sup&gt;+&lt;/sup&gt;e&lt;sup&gt;-&lt;/sup&gt;-colliders, such as the proposed Future Circular Collider electron-positron (FCC-ee) at CERN operating as a Higgs and electroweak factory, necessitates new implementations while enabling innovative approaches in &amp;tau; lepton reconstruction. In the FCC dataset, the &amp;tau; lepton plays a crucial role in many physics topics. Focusing on the IDEA detector concept at the FCC-ee, machine learning (ML) approaches for jet flavor tagging are studied. Additionally, explicit reconstruction algorithms are employed for tagging the decay mode of &amp;tau; leptons from its decay products on the jet level.&lt;/p&gt;

&lt;p&gt;In the study about using ML for identifying the flavor of Z boson decay jets, the existing, state-of-the-art Particle Transformer Network shows very good performance with very low false positive rates in quark jet suppression against Z &amp;rarr; &amp;tau;&lt;sup&gt;+&lt;/sup&gt;&amp;tau;&lt;sup&gt;-&lt;/sup&gt; signal samples. A more simplistic feed-forward neural network is compared against the transformer model and shows worse performance with an increased false positive rate of two orders of magnitude.&lt;/p&gt;

&lt;p&gt;&lt;br&gt;
Using an explicit reconstruction approach for the &amp;tau; decay mode identification, the combination with the reconstruction of intermediate states, like the neutral &amp;pi;&lt;sup&gt;0&lt;/sup&gt; meson or the &amp;rho;(770) meson is proposed. The performance of this method is evaluated in dependence on multiple cuts on the jet properties, aiming at optimizing the purity of the identified decay&lt;br&gt;
modes and investigating the efficiency-purity-relation. The proposed techniques promise good performance in &amp;tau; reconstruction at FCC-ee but also further the need for a full simulation of the Innovative Detector for Electron-positron Accelerator (IDEA) detector to find final conclusions on the limitations of &amp;tau; lepton reconstruction, as the current fast simulation shows limitations for the reconstruction of &amp;tau; leptons. Additionally, alternative approaches to the tasks at hand are proposed.&lt;/p&gt;</subfield>
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