Master Theses

We present the computation of the trilinear Higgs self-coupling in an extension of the Standard Model (SM) of particle physics that incorporates supersymmetry, namely the Minimal Supersymmetric Standard Model (MSSM). As a simplification, only the top and bottom sector and their superpartners (stop and sbottom) are included and in the calculation external momenta are set to zero..

The Higgs sector provides a promising area to search for additional sources of CP violationbeyond the Standard Model, which are required to explain the baryon asymmetry observedin our universe.This thesis investigates the sensitivity to possible CP-violating contributions in the Higgs-boson-tau-lepton Yukawa coupling, studying H → τ+τ− decays at a future linear e+e−collider operating at a center of mass energy of √s= 250 GeV and using the InternationalLarge Detector (ILD) concept. The analysis considers Higgs-strahlung events, e+e−→ ZH,with the associated Z boson decaying into a pair of muons and the tau leptons associated withthe Higgs boson undergoing hadronic one-prong decays τ± → ντπ± or τ± → ντρ± → ντπ±π0.Simulated event samples corresponding to an integrated luminosity of 2 ab−1 are analyzed.The CP structure of the Higgs-tau Yukawa interaction is parametrized by the CP-mixing angleψτCP. [...]

The LUXE experiment at the European XFEL will probe quantum electrodynamics (QED) inthe strong-field regime by measuring the energy spectrum of nonlinear Compton-scatteredelectrons. Its Electron Detection System (EDS) resolves this spectrum using a Cherenkov strawdetector with silicon photomultiplier (SiPM) readout. [...]

A study for the associated production of a Higgs boson with a top quark pair $(t\bar{t}H)$ in the fully hadronic final state is presented, focusing on the H → $b\bar{b}$ decay channel using proton-protoncollision data collected by the CMS experiment during Run 3 in 2024. Resolving the jet-parton assignment task in this high jet multiplicity environment represents a major source of combinatorial ambiguity. [...]

One of the main constraining factors in IceCube’s ability to detect neutrino point sources is angular resolution. Muon track reconstruction is limited by the current knowledge of theoretical properties of ice and the detector responses. [...]

This thesis presents measurements of charm and beauty quark production in proton–proton collisions at a center-of-mass energy of √s = 5 TeV using the CMS detector at the LargeHadron Collider at CERN.Heavy-flavor production cross sections test perturbative Quantum Chromodynamics and constrain parameters such as heavy-quark masses and the proton parton distribution functions.In this work, the double-differential production cross sections of D∗ mesons are measured as functions of the transverse momentum pT and the absolute rapidity |y|, reaching very low transverse momenta. The kinematic region covered by CMS is complementary to previous measurements at the LHC. [...]

This thesis presents a precision measurement of the CP properties of the Higgs tau Yukawa coupling, focusing on the H → τ τ → μa3pr 1 +3ν decay channel with ggF and VBF production.The study uses proton–proton collisions data recorded by CMS in 2022 and 2023 at √s = 13.6TeV, corresponding to an integrated luminosity of 62.4 fb−1. The CP-mixing angle αHττ is determined via the coplanarity angle ϕCP . [...]

Astroparticle physics arose from the desire to study and understand different mechanisms of particle production, their acceleration to the highest energies, and transport over cosmic scales. By observing high-energy particles from the cosmos, this field probes the extremes of fundamental interactions and investigates the nature of dark matter and dark energy, therefore exploring the origins of our universe. [...]

Among other restrictions, vacuum stability is a theoretical constraint for vacuumconfigurations in BSM theories to be allowed or excluded. But due to multidimensionalfield spaces, computing the vacuum stability is a challenging task. [...]

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. [...]