Ph.D. Theses

This thesis presents the first global interpretation of the measurements of doubledifferentialcross sections of inclusive jet and top quark-antiquark pair (tt) productionin proton-proton collisions at the Large Hadron Collider (LHC) at the center ofmass energy of √s = 13TeV, together with inclusive measurements in Deep Inelasticelectron-proton Scattering (DIS) at HERA. The LHC data have been recordedby the Compact Muon Solenoid (CMS) experiment in 2016, and correspond to theintegrated luminosity of 33.5 fb−1 for inclusive jet measurement or 35.9 fb−1 for the ttmeasurement.This novel analysis is performed at next-to-leading order (NLO) of perturbative quantumchromodynamics (QCD), where the inclusive neutral and charged current DISmeasurements at HERA, the CMS jet measurements and the normalized triple-differentialcross sections of tt production are used together to constrain the parametersof QCD and impose constraints on new physics. [...]

In this thesis, measurements are presented using proton-proton collision data at s =13 TeV collected by the CMS experiment in the years 2016, 2017, and 2018, corresponding to an integrated luminosity of 138 fb−1. New results on single top quark production in association with a Z boson (tZq) are presented. [...]

This thesis deals with calculations of higher-order corrections in perturbative quantum chromodynamics(QCD). The two-mass contributions to the 3-loop, polarized twist-two operator matrixelements (OMEs) A(3),PSQq and A(3)gg,Q are calculated. [...]

Axions and axion-like particles are very well-motivated candidates for physics beyond the Standard model, which can be probed by multiple existing and projected experiments and astrophysical observations. Theoretical determination of the relevant low energy axion interactions is essential for guiding the corresponding experimental and observational efforts. [...]

he goal of this dissertation was to investigate a reliable single-shot pulse duration diagnostic tool for the pulse duration and wavelength range delivered at the Free Electron LAser of Hamburg (FLASH). At Self-Amplified-Spontaneous-Emission-based free-electron lasers (FELs), the radiation parameters - duration, arrival time, energy, spectrum, and spatial distribution - differ for each pulse [...]

The understanding of the theory of strong interactions in the context of the Standard Model is of great interest to particle physics and its developments. The measurements andthe improvement of the theoretical predictions would allow us to get closer to future findings of new physics by discriminating better between backgrounds produced mainly by stronginteractions. [...]

We consider the renormalization of operator matrix elements for exclusive hard scattering processes in the chiral limit in the $\overline{\text{MS}}$-scheme. For such processes, mixing with total derivative operators has to be taken into account. [...]

A plasma can sustain electric fields orders of magnitude larger than those attainable with the conventional radio-frequency (RF) technology typically used in particle accelerators, which are limited to ∼ 100 MV/m due to electrical breakdowns occurring at the metallic boundary of the accelerating structures. In a particle-beam-driven plasma-wakefield accelerator (PWFA), a charge-density wake sustaining field gradients in excess of GV/m is driven by the passage of a relativistic high-intensity particle bunch through a plasma. [...]

In this thesis, a measurement of the differential cross section for hadronically decayingW and Z bosons produced in proton-proton collisions is presented. Decay productsof the vector bosons with very high transverse momentum pT are collimated in themomentum direction of the mother particle and are merged into a large cone-size jetwith the characteristic inner structure. [...]