Electroweak Physics at the Large Hadron Collider with the ATLAS Detector : Standard Model Measurement, Supersymmetry Searches, Excesses, and Upgrade Electronics

This thesis discusses searches for electroweakly produced supersymmetric partners of the gauge and the Higgs bosons (gauginos and higgsinos) decaying to multiple leptons, using pp collisions at sqrt(s) = 13 TeV. The thesis presents an in-depth study of multiple searches, as well as the first 13 TeV cross section measurement for the dominant background in these searches, WZ production. Two searches were performed using 36.1/fb of data: the gaugino search, which makes use of a novel kinematic variable, and the higgsino search, which produced the first higgsino limits at the LHC. A search using 139/fb of data makes use of a new technique developed in this thesis to cross check an excess of data above the background expectation in a search using a Recursive Jigsaw Reconstruction technique. None of the searches showed a significant excess of data, and limits were expanded with respect to previous results. These searches will benefit from the addition of luminosity during HL-LHC; however, the current detector will not be able to withstand the increase in radiation. Electronics for the detector upgrade are tested and irradiated to ensure their performance. Front Matter ....Pages i-xxiii Introduction (Elodie Resseguie)....Pages 1-2 Theoretical Framework (Elodie Resseguie)....Pages 3-33 LHC and the ATLAS Detector (Elodie Resseguie)....Pages 35-53 HL-LHC Inner Detector Upgrade (Elodie Resseguie)....Pages 55-85 \(W^\pm Z\) Cross-Section Measurement at \(\sqrt{s} = 13\) TeV (Elodie Resseguie)....Pages 87-119 Searches for Electroweak SUSY: Motivation and Models (Elodie Resseguie)....Pages 121-129 Search for Wino-Bino Production Decaying via WZ at \(\sqrt{s}=13\) TeV (Elodie Resseguie)....Pages 131-173 Studying the Excess in the Recursive Jigsaw Reconstruction (RJR) Search Using the Emulated RJR (eRJR) Technique (Elodie Resseguie)....Pages 175-204 Search for Wino-Bino Production Using the Emulated Recursive Jigsaw Reconstruction Technique with Run 2 Data (Elodie Resseguie)....Pages 205-255 Search for the EWK Production of Compressed SUSY with Soft Leptons (Elodie Resseguie)....Pages 257-294 Future Work: Search for Compressed Wino-Bino Production in the Three Lepton Final State (Elodie Resseguie)....Pages 295-310 Conclusion (Elodie Resseguie)....Pages 311-313 Back Matter ....Pages 315-322