Ph.D. Theses

The nature of dark matter (DM) remains one of the most compelling mysteries in modernphysics. Despite DM exceeding the visible (baryonic) matter by a factor of four, itsorigin and properties are yet to be understood. [...]

Context: The main obstacle of quantum computing on its way to scalability is the noisy nature of current hardware. Various types of errors lead to incorrect computational results,and measures such as quantum error mitigation are needed to counteract these errors. [...]

Modern particle physics is extremely reliant on advanced instrumentation, in particular, detectors. One of the key technologies for current and future experiments is semiconductor detectors. [...]

Measuring the polarisation of an electromagnetic wave can be a useful tool to study the emission source of the wave and the interactions of the wave during its propagation. While in the optical spectrum a measurement can be done with foils that filter polarisation directions, a measurement in the X-ray range requires precisely manufactured crystals. [...]

The emergence of powerful synchrotron sources, fast pixel detectors, and the increasingavailability of high-performance computing has facilitated the acquisition and analysisof high-quality, large-volume diffuse scattering data, providing insights into the realstructures of disordered crystals that were not previously possible. However, its ap-plication to studying local structural order in thin films remains largely unexplored.This limitation arises from the strong substrate contributions, which obscures the weakdiffuse scattering signals from the film, as well as the restricted reciprocal space cov-erage and resolution inherent in grazing incidence X-ray diffraction. [...]

This thesis presents a comprehensive study of the single top quark production in association with a WZ boson pair (tWZ), culminating in the first observation of this process. Measurements of rare processes are crucial to improve our understanding of the Standard Model (SM) and improve the sensitivity to loop-induced new physics. [...]

Die Entdeckung des Higgs-Bosons 2012 am LHC bestätigte das Standardmodell als führende Theorie zur Beschreibung fundamentaler Teilchenwechselwirkungen. Mit größeren Datensätzen konnten die Eigenschaften des Higgs-Bosons immer präziser untersucht werden. [...]

A search for the production of a pair of Higgs bosons ($HH$) via vector-boson fusion (VBF) in the Lorentz-boosted kinematic regime with subsequent decay of the Higgs bosons into four bottom quarks is presented. The analysis is based on 140~fb$^{-1}$ of proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider (LHC), at a center-of-mass energy of $\sqrt{s} = 13$~TeV. [...]

In this thesis, we study different aspects of heavy-quark effects in factorization and resummation using the methods of effective field theories. As the quark masses are much lighter than the hard scale of processes at the LHC, they are considered subleading and usually neglected. [...]

Optische Beobachtungen mit großem Sichtfeld und hoher Kadenz haben jedes Jahr zur Entdeckung mehrerer neuer Quellen am Transientenhimmel geführt. Es wird vermutet, dass bestimmte Arten von Transienten, wie z. [...]