Books

Two key measurements and two phenomenological studies of top quark pair ($\mathrm{t\bar{t}}$) production with the CMS experiment at the CERN Large Hadron Collider are presented. They include the first measurement of the $\mathrm{t\bar{t}}$ cross section at the new energy frontier, a detailed analysis of the $\mathrm{t\bar{t}}$ threshold culminating in the first observation of $\mathrm{t\bar{t}}$ bound state effects, and searches for new physics in $\mathrm{t\bar{t}}$ final states, such as heavy scalars, pseudoscalars or Axion-Like Particles.The inclusive $\mathrm{t\bar{t}}$ production cross section $\sigma_{\mathrm{t\bar{t}}}$ is measured for the first time at the world-record energy of $\sqrt{s} = 13.6\,\mathrm{TeV}$, using $1.21\,\mathrm{fb}^{-1}$ of early LHC Run 3 data. [...]

AbstractThis thesis both proposes and experimentally explores the opportunity to operate TransitionEdge Sensors (TES) as detectors for Dark Matter (DM)-scattering by simultaneouslyemploying them as target and sensor. By exploiting their microcalorimetric capabilitiesand sensitivity to low energy depositions, competitive limits can be set on low mass DMinteractions based on electron scattering. [...]

The Tangerine group at DESY, Hamburg, investigates the potential of Monolithic Active PixelSensors (MAPS) manufactured in a novel 65 nm CMOS imaging process with small collectionelectrode design, as a candidate technology for vertex and tracking detectors in future leptoncollider experiments. One of the activities undertaken to explore the technology is the char-acterisation of prototypes through the analysis of test beam measurements. [...]

Future e+e− colliders, such as the FCC-ee, aim to test the Standard Model to the ultimateprecision. This requires synergistic progress in detector technology and data analysis techniques.This thesis comprehensively presents the interlinked efforts targeting these goals.Jet flavour identification algorithms play a crucial role in maximally exploiting the physicspotential of the FCC-ee, particularly in the Higgs and electroweak sectors. [...]

The FCC-ee is the first stage of a two stage project which would envision a 92 km tunnelbeing used for an electron-positron collider experiment starting around 2045, and a proton-proton collider in the 2070’s. The FCC-ee offers unprecedented precision tests of the StandardModel, owing to its clean leptonic collision environment and exquisite luminosity [...]

Version 3.1.72025-09-03 RELEASE: version 3.1.72025-08-22 Bug fix: minor glitch in internal string handling2025-07-28 Major overhaul of EVA (equivalent vector boson approx.): - revalidation of structure functions from Whizard v1.91 - EVA is available for polarized lepton beams - Different EVA modes/approximations avail. (2507.19285)2025-07-01 Different variants of complex-mass scheme for O'Mega SM2025-05-07 Bug fix: external OLP event generation for polarized beams2025-04-30 Minimal compiler versions: OCaml 4.11, gfortran 11.1.0 Compatibility with macOS 15.4 and XCode 16.3

This thesis presents precise determinations of two fundamental parameters of the stan-dard model (SM), the strong coupling constant αS (mZ) and the top quark mass mtalong with its width Γt. These contribute importantly to constraints on the stabilityof the SM electroweak vacuum.For the determination of αS (mZ), CMS inclusive jet measurements using LHC proton-proton (pp) collisions at centre-of-mass energies √s = 2.76, 7, 8, and 13 TeV are anal-ysed together, for the first time. [...]

Gauge-mediated supersymmetry breaking models provide a compelling framework for the search for a supersymmetric partner of the tau lepton ($\widetilde{\tau}$) with a macroscopic lifetime. In such scenarios, $\widetilde{\tau}$ can decay to tau lepton displaced from the primary proton-proton interaction vertex. [...]