Bryan Kortman, promovendus aan het Nikhef, verdedigt zijn proefschrift vrijdag 3 oktober 2025 om 12.30 aan de Universiteit Twente.
Interfering with the Higgs Boson – Lifetime Measurements and Effective Field Theory Interpretations of Higgs Boson Decays into Charged Vector Bosons at the LHC using the ATLAS Experiment
The Standard Model (SM) is the theoretical framework in particle physics. Developed to explain matter at its most fundamental level, the SM describes elementary particles and their interactions via three fundamental forces: the strong, weak, and electromagnetic forces. This model has been tested and verified across a vast array of experiments and energy scales, consistently showing excellent agreement with observed data. However, despite its successes, the SM falls short in explaining several key aspects of the universe such as dark matter, gravity, and the imbalance between matter and antimatter. These and more unresolved questions suggest the SM is still incomplete, sparking ongoing research aimed at the development of a more comprehensive theory of particle physics.
Historically, theoretical advancements have often led the way in particle physics, with theories predicting new subatomic particles and experiments designed to confirm these predictions. However, during the most recent runs of the Large Hadron Collider (LHC), researchers did not find evidence for supersymmetry, a widely researched theoretical framework that many believed would be the next breakthrough after decades of development. As a result, the direction of current research has shifted. Instead of primarily searching for theoretical predictions, scientists are now focused on analysing data directly, in search of a deviation from SM predictions that might hint at new physics.
This thesis explores two promising avenues for uncovering new physics using proton-proton collision data at a centre-of-mass energy of 13 tera-electronvolt, collected during Run-2 of the LHC. First, off-shell Higgs measurements offer a window into the rarely observed high-mass regime of the Higgs boson. This allows the measurement to estimate the Higgs lifetime and explore potential influences from undiscovered particles by directly measuring Higgs couplings. Since new physics models include extra scalars or a composite Higgs, the off-shell mechanism can deviate from the SM, altering the Higgs lifetime.
Second, interpretations of Higgs measurements based on SM Effective Field Theory (SM-EFT) try to reveal possible higher-dimensional operators, which could point to BSM physics through the addition of a heavy new particle.
Both methods leverage the quantum interference occurring in the production and decay of the Higgs boson and other SM particles. In these analyses, the observed interference patterns in final states are utilized to explore the potential existence of physics beyond the SM.
De promotie vindt plaats in de Prof. dr. G. Berkhoff-Zaal, Waaier 4, Enschede.
Meer informatie en een link naar de livestream op de website van de Universiteit Twente.
Promotoren: prof. dr. T.A. du Pree, prof. dr. P. Ferrari en prof. dr. W. Verkerke
Contact: Bryan Kortman
