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Upgrade of the ATLAS Experiment Inner Tracker and related physics perspectives of the Higgs boson decay into two b quarks

Abstract : By 2027, the LHC will enter its high luminosity regime, providing protons protons collisions at an unprecedented rate. The LHC experiments whill have to be upgraded to cope with this higher data rate. The new ATLAS Inner Tracker (ITk) will allow a better identification of b-quarks and interesting physics signature with b-quarks in the final states such as the Higgs trilinear coupling will be reachable. The work performed during this thesis consisted in testing planar pixel sensors for the ITk, as well as optimizing b-tagging algorithms. In parallel, a study on the radiation damage on silicon pixel sensors have been performed. The radiation hardness of silicon sensors plays a determinant role as it allows them to be efficient in the highly radiative environment at LHC. Understanding the impact of radiation in silicon sensors is a major challenge and a radiation damage digitizer which models radiation damage effects in ATLAS Monte Carlo simulations is currently developed by the ATLAS experiment. Three ITk silicon planar pixel sensors productions of LPNHE and FBK have been developed, produced and tested on beam. Sensors from these three productions aim to be part of the ITk and have to demonstrate good performance after being irradiated at high fluences. Several technological designs have been investigated, such as temporary metal biasing option and active edges which maximize the geometrical acceptance of the sensors. The optimization of b-tagging SV1 algorithm (a secondary-vertex based algorithm) will be pre- sented as well as a study on the extrapolation of b-tagging performances at high pT.
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Submitted on : Thursday, January 30, 2020 - 2:30:12 PM
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Audrey Ducourthial. Upgrade of the ATLAS Experiment Inner Tracker and related physics perspectives of the Higgs boson decay into two b quarks. Physics [physics]. Université Sorbonne Paris Cité, 2018. English. ⟨NNT : 2018USPCC212⟩. ⟨tel-02461104⟩



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