Master Theses

As the search for physics beyond the Standard Model continues, this thesis presentsan analysis in the long-lived particle (LLP) supersymmetry sector. A Boosted DecisionTree (BDT) classifier was developed to enhance the search for long-lived supersymmetricpartner particles of the tau lepton (stau) particles in the muon-hadronic tau channel at theCMS detector in LHC, motivated by Gauge Mediated Supersymmetry Breaking (GMSB)scenarios. [...]

This thesis evaluates a b-tagging algorithm optimized to identify low pT (soft) b-hadrons in theATLAS experiment at the LHC. The algorithm, called the NewVrtSecInclusiveTool, reconstructssoft secondary vertices (SSVs), which can be connected to the decay of a soft b-hadron [...]

(di-Higgs) events using simulated data from the ATLAS detector at the Large Hadron Collider ata center-of-mass energy of √s = 13TeV and an integrated luminosity of 140 fb−1. In the studiedchannel, one Higgs boson decays into a bottom quark-antiquark pair (b¯b), the other into two photons(γγ) [...]

In the endeavour to understand the fundamental components of the universe, the search for newparticles beyond the Standard Model of particle physics is a pivotal task. Axion-like particles (ALPs)are among the prime targets of this search, arising in various theoretical frameworks, includingquantum chromodynamics, supersymmetric extensions of the Standard Model of particle physics orstring theory. [...]

Palladium nanoparticles are widely studied in various fields of science. In biology, Pd parti-cles are studied for possible medical applications, in chemistry the particles are often synthe-sised in solution and then applied to a support via, for example, spin coating. [...]

Catalysts have a wide field of applications, for example, they play an important rolein producing chemicals and for renewable energies. Thus it is of great interest tomake them more efficient and to increase their lifetime [...]

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. [...]

Monolithic Active Pixel Sensors (MAPS) produced in CMOS image sensor (CIS) technology are a promising candidate for meeting the stringent requirements for vertex detectors at future lepton colliders. Recently, a 65 nm CIS process has become available to the high-energy physics community, offering enhanced integration density and lowered power consumption. [...]

We present a precision computation of the trilinear Higgs boson self-coupling \(\lambda_{hhh}\) in the Standard Model (SM) and the Type-II Two-Higgs-Doublet-Model (\text{THDM}) in the alignment limit, both with vanishing external momenta for the vertex, employing a fully on-shell renormalization scheme. Our analysis includes all one-loop corrections and, for the first time to our knowledge, the dominant two-loop top- and bottom-Yukawa contributions of \(\mathcal{O}(N_c^2)\). [...]

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 col-liders. [...]