TY  - THES
AU  - Gonzalez Rodrigues, Marcus
TI  - Search for the production of a pair of highly Lorentz-boosted Higgs bosons via vector-boson fusion in final states with four bottom quarks with the ATLAS experiment
PB  - University of Hamburg
VL  - Dissertation
M1  - PUBDB-2025-05033
SP  - 188
PY  - 2025
N1  - Dissertation, University of Hamburg, 2025
AB  - A search for the production of a pair of Higgs bosons (HH) via vector-boson fusion (VBF) in the Lorentz-boosted kinematic regime with subsequent decay of the Higgs bosons into four bottom quarks is presented. The analysis is based on 140 fb<sup>−1</sup> of proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider (LHC), at a center-of-mass energy of √s = 13 TeV. The results were interpreted in terms of both non-resonant and resonant production of Higgs-boson pairs. Non-resonant VBF HH production is predicted by the Standard Model (SM); the production cross-section is, however, significantly enhanced for anomalous, non-SM values for the trilinear Higgs-boson self-coupling and the quartic coupling between two Higgs bosons and two vector bosons, parametrised as κ<sub>\l</sub> and κ<sub>2V</sub>, respectively. Resonant VBF HH production is predicted only by extensions of the SM. In this thesis, the resonant HH production via the decay of a new heavy scalar particle originating from the vector-boson scattering was considered. No significant deviation of the data from the expected background was observed. Hence, in the non-resonant search, limits on the κ<sub>2V</sub> and κ<sub>\l</sub> couplings were set at 95% confidence level. In the resonant search, upper limits on the signal cross-section were derived for intermediate masses ranging from 1.0 TeV to 5.0 TeV under the assumptions of a narrow- and broad-resonance widths. In the model-dependent broad-width scenario, a composite Higgs benchmark has been considered. In addition to these results, which have been published in 2024, the relevant details of a successive on-going ATLAS analysis using additionally data collected in 2022 and 2023 at √s = 13.6 TeV and using more modern tools to identify the H → b―b decays is discussed here. Finally, a proof-of-principle study using a transformer-based machine-learning algorithm to discriminate signal from background events in triple Higgs-boson searches is also shown in this thesis. The even rarer production of three Higgs bosons has been gaining significant interest since it provides unique access to the quartic Higgs-boson self-coupling.
KW  - 530: Physik (autogen)
LB  - PUB:(DE-HGF)11
DO  - DOI:10.3204/PUBDB-2025-05033
UR  - https://bib-pubdb1.desy.de/record/641372
ER  -