Master Theses

The 2012 discovery of the 12 GeV Higgs boson at the LHC, and of no other particle since then, have brought a consensus to the particle physics community that an e+e- Higgs factory is the highest priority next collider. However, Higgs measurements suffer from the loss of undetected neutrino energy due to semi-leptonic decays (SLDs) in the most common decay mode H to b anti-b. [...]

The probabilistic nature of photoemission, combined with the exploration of large multidimensional parameter spaces–including momentum, energy, time and spin polarization–necessitates time-intensive data acquisition to ensure statistical robustness. These measurements are especially important for capturing ultrafast phenomena, where pulsed light sources, such as free-electron lasers (FELs), become indispensable due to their ability to deliver high-brightness, ultrashort X-ray pulses. [...]

A top priority of future collider programs is to measure the value of the Higgs self-coupling λ. Through double Higgs production (ZHH), this is possible by direct measurement at lepton colliders. [...]

The Phase II upgrade of the ATLAS detector will prepare it to handle the 2.5–fold increase in instantaneous luminosity of the High Luminosity LHC project starting in 2028. The upgrade will also involve the tracking sub-system of the ATLAS detector to be replaced by the Inner Tracker (ITk), which is made up of a closer-to-beam-line Pixel and acircumscribing Strip detector. [...]

The international particle physics community has identified an e+e− Higgs factory as the highest-priority next collider. Such a facility would enable the production of a substantial number ofW bosons. [...]

The studies in this thesis are motivated by the measurement of the top quark Yukawa coupling Ytrelative to the SM value in the dileptonic decay channel of top-antitop (t¯t) pairs at the ATLAS experiment. The used (simulated) data correspond to the proton-proton collision data recorded between 2015 and 2018 at √s=13 TeV with an integrated luminosity of 140 fb−1. [...]

Pathological iron accumulation in the brain is a hallmark of several neurodegenerative diseases like Parkinson’s, Alzheimer’s and Huntington’s disease. Magnetic resonance imaging offers a unique non-invasive method to measure brain iron because iron affects the spin relaxation parameters of water protons and magnetic susceptibility of the brain tissue [...]

The Dark Photon is a hypothetical particle that can be possibly detected in the experiment because of its kinetic mixing with the ordinary, visible photon. In theories where dark matter is explained by the existence of a ’dark sector’, interacting with the visible sector of the Standard Model via gravitation, the photon of the dark sector, the Dark Photon (A_D ), might be the only visible manifestation of the dark sector. [...]

In this thesis, it is shown that ocean-generated microseism significantly impacts the synchronisation performance of the European X-ray free-electron laser (XFEL), which is based on a high-energy linear accelerator. Using superconducting technology, it generates hard X-ray pulses at megahertz frequencies. [...]