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Etalonnage du calorimètre électromagnétique d'ATLAS et recherche de la production de paires de bosons de Higgs dans l'état final bbyy avec les données de Run 2 et Run 3 collectées par le détecteur ATLAS auprès du LHC

Year: 2025
Type: dissertation
Abstract: After ten years of discovery of the Higgs boson, the LHC continues to measure the properties of the Higgs boson in greater details. The determination of the Higgs self-coupling could reveal where the new physics lies and shed light on the history of the early universe. This thesis presents the determination of the in-situ scale and resolution as well as for ATLAS electron and photon energy calibration. The resulting precision for Run 3 achieves the one for Run 2. The determination of the AtlFast3-Geant4 correction factors is also described, which is vital to maintain the achieved precision in the calibration for samples simulated with AtlFast3. A new di-Higgs production analysis in the bbyy decay channel with data collected in Run 2 and partial Run 3 period is presented. A significance of 0.8 sigma on muHH is observed, while 1.0, sigma expected. An observed 95% CL upper limit of 3.8 on muHH is set against the SM HH production hypothesis. The expected upper limit is muHH < 2.6~(3.7) against no or SM HH production hypothesis. The observed (expected) 95% CL intervals are -1.7~(-1.8) < kappa_lambda < 6.6~(6.9) and -0.5~(-0.4) < kappa_{2V} < 2.6~(2.6) respectively for klambda and kVV.
Author: Hsu, Tao
Language: English
Open Access status: green
OpenAlex ID: W7108248624
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