Books

In the Minimal Supersymmetric Standard Model (MSSM), the mass of the SM-like Higgs boson can be predicted in terms of the model parameters and therefore used as a precision observable to constrain the MSSM parameter space. The precise prediction of the lightest MSSM Higgs boson mass in scenarios with one or several heavy supersymmetric particles requires the resummation of higher-order logarithmic contributions obtained within an effective-field-theory (EFT) approach. [...]

This work investigates if and how photoelectron diffraction might become a suitable tool to measure structural changes of small molecules in the gas-phase with femtosecond temporal and angstrom spatial resolution. Molecular-frame photoelectron angular distributions (MFPAD) of O(1$s$)-, S(2$p$)- and F(1$s$)-electrons from carbonyl sulfide and fluoromethane molecules have been measured in photoelectron-photoion coincidence experiments at the synchrotron radiation sources DORIS and PETRA III (kinetic energy of photoelectrons: 16 eV < E$_{\mathrm{PE}}$ < 283 eV). [...]

In this thesis, we perform a comprehensive study of Big Bang nucleosynthesis constraints on different dark-sector models with $\mathrm{MeV}$-scale particles which are neither fully relativistic nor fully non-relativistic during all relevant temperatures. To this end, we derive a generic set of equations that can be used to determine the light-element abundances for many different dark-sector scenarios. [...]

In this thesis, the rst experimental determination of the running of the top quarkmass is presented. The running is extracted from a measurement of the dierentialtop quark-antiquark (tt) production cross section as a function of the invariant massof the tt system, mtt. [...]

In this thesis, two searches for new heavy particles with top quarks in the final stateare presented. They are based on data recorded by the CMS detector in the years 2016and 2017, respectively.In the first part of this thesis, the first search for pair-produced leptoquarks (LQs)decaying to top quarks and muons is presented [...]

Magnetic field sensors can be used for compass applications, to measure electrical cur-rents or to determine position and speed of objects. Layered thin-film sensors based onthe giant or tunneling magnetoresistance (GMR or TMR) are predestined for portabledevices where their small size, high effect strength and low power consumption are crucial.Through the use of oblique-incidence deposition (OID) it is possible to tailor the magneticand magnetoresistive properties of the sensors in an easy-accessible and flexible way tothe needs of an application. [...]

This thesis describes two types of light-matter interactions in magnetic thin films. In the first part, it focuses on the resonant interaction of hard X-rays with 57Fe nuclei in a microstructured magnetic element. [...]

A detailed study of the near-surface composition and structure of Nb, the current state-of-the-art material for superconducting radio-frequency accelerator (SRF) cavities, is of extreme importance in order to understand the consequences of different treatments applied during their production as well as its effects in conditions resembling real operation. Recently, different thermal treatments involving the presence of nitrogen achieved remarkable performance increases of such devices, however, the physical and chemical phenomena involved are still elusive. [...]