04371nam 22007095 450 991072627460332120230523094746.09783031304668(electronic bk.)978303130465110.1007/978-3-031-30466-8(MiAaPQ)EBC30550654(Au-PeEL)EBL30550654(OCoLC)1380464631(DE-He213)978-3-031-30466-8(BIP)089230907(PPN)270614346(CKB)26761002200041(EXLCZ)992676100220004120230523d2023 u| 0engurcnu||||||||txtrdacontentcrdamediacrrdacarrierA Search for Exotic Higgs Decays Or: How I Learned to Stop Worrying and Love Long-Lived Particles /by Jackson Burzynski1st ed. 2023.Cham :Springer International Publishing :Imprint: Springer,2023.1 online resource (201 pages)Springer Theses, Recognizing Outstanding Ph.D. Research,2190-5061Print version: Burzynski, Jackson A Search for Exotic Higgs Decays Cham : Springer International Publishing AG,c2023 9783031304651 The Standard Model -- Physics Beyond the Standard Model -- The Large Hadron Collider and the ATLAS Detector -- Event Reconstruction -- Reconstruction of Long-Lived Particle Decays.This work describes a search for exotic decays of the Higgs boson to two long-lived, neutral, spin-0 particles which subsequently decay to pairs of b quarks, giving the striking signature of displaced hadronic jets in the ATLAS inner detector. Several other ATLAS searches have probed this decay topology previously, excluding branching ratios of the Higgs boson to long-lived particles (LLPs) of more than 10% for proper lifetimes greater than 100mm. These searches relied on dedicated triggers designed to select events with LLPs decaying in the ATLAS calorimeter or muon spectrometer. The lack of an equivalent trigger for LLP decays in the ATLAS inner detector has been a limiting factor in probing LLP lifetimes less than 100mm. To circumvent the difficulty of triggering on LLP decays, the search presented in this thesis exploits the ZH associated production mode, relying on leptonic trigger signatures to select interesting events. This is the first search for Higgs boson decays into LLPs to exploit this analysis methodology and additionally makes use of several novel methods for both background rejection and background estimation. No excess over Standard Model predictions is observed, and upper limits are set on the branching ratio of the Higgs boson to LLPs . Depending on the mass of the LLP, branching ratios greater than 10% are excluded for lifetimes as small as 4mm and as large as 100mm, probing an important gap in the ATLAS exotic Higgs decay programme. In comparison to the previous searches for Higgs decays to LLPs, these are among the most stringent limits placed on this scenario, and for LLPs with masses below 40 GeV these results represent the strongest existing constraints on the branching ratio of the Higgs boson to LLPs in this lifetime regime.Springer Theses, Recognizing Outstanding Ph.D. Research,2190-5061Particles (Nuclear physics)Particles (Nuclear physics)Quantum field theoryQuantitative researchParticle acceleratorsParticle PhysicsElementary Particles, Quantum Field TheoryData Analysis and Big DataAccelerator PhysicsPhysicsScienceParticles (Nuclear physics)Particles (Nuclear physics)Quantum field theory.Quantitative research.Particle accelerators.Particle Physics.Elementary Particles, Quantum Field Theory.Data Analysis and Big Data.Accelerator Physics.539.721539.721Burzynski Jackson1359476MiAaPQMiAaPQMiAaPQ9910726274603321A Search for Exotic Higgs Decays3373975UNINA