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Development of tau selection techniques for the Higgs boson produced associated to a pair of top quarks and decaying into tau leptons

Abstract : The CMS (Compact Muon Solenoid) experiment aims at studying the results of proton collisions produced by the LHC (Large Hadron Collider) at CERN. The discovery of the Higgs boson is a great leap forward as the corresponding mechanism states that particles masses are the result of an interaction with the associated scalar field. The nature of that field is being studied in details and this will occupy the CMS collaborators for the next years. The characterization of the Higgs sector as well as the search for new physics will require the full capabilities of the LHC. Upgrades have been done along the way to reach much higher luminosities (>5x1034cm-2s-1). The CMS experiment deploys a 14000 tones detector equipped with advanced electronics to track and identify precisely all the particles produced from the collisions. Although CMS showed an excellent performance, it underwent upgrades, which include a new data acquisition system to fully exploit high luminosity conditions.The thesis work focuses on taking advantage of the newer analysis and selection techniques to search for tau leptons coming from Higgs which was produced associated to two tops (ttH). The ttH production mode is important to characterize the properties of the Higgs boson and in particular its coupling to top quarks, to which the ttH process has direct access. The Higgs to tau leptons is of particular interest as it probes the Higgs coupling to fermions. Given the mass of the Higgs, the tau decay mode is certainly favored but still represents challenging aspects in both selection and reconstruction techniques. The ttH analysis is particularly challenging given the complexity of final states and makes use of the latest signal extraction techniques. Since its observation in 2018, this analysis is one of the main priorities of the CMS experiment, and the Cristina Martin Perez plays a major role in the full Run 2 legacy paper preparation.Besides, this thesis focuses on the development of a dedicated tau selection algorithm, which had never been achieved with the electronics layers of the data acquisition system. A new trigger system was commissioned with proton collisions data and is being used as the baseline system starting 2016. Cristina Martin Perez plays a leading role in the performance studies and optimization of this trigger.
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Submitted on : Friday, December 18, 2020 - 2:25:04 PM
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  • HAL Id : tel-03082008, version 1

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Cristina Martin Perez. Development of tau selection techniques for the Higgs boson produced associated to a pair of top quarks and decaying into tau leptons. High Energy Physics - Experiment [hep-ex]. Institut Polytechnique de Paris, 2020. English. ⟨NNT : 2020IPPAX065⟩. ⟨tel-03082008⟩

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