Giovanni BARTOLINI, Search for the associated production of Higgs boson and top quark pairs in multijet events and calibration of the b-jet trigger for the ATLAS detector at the LHC

vendredi 6 nov. 2020, 15:00 → 18:00 Europe/Paris

Amphi (CPPM)

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Meeting ID: 949 2616 5363

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Composition du jury :

Stephen SEKULA Rapporteur Southern Methodist University
Florencia CANELLI Rapporteuse Physik-Institut of the University of Zurich
Frédéric DÉLIOT Examinateur DPhP IRFU CEA Paris-Saclay

Cristinel DIACONU Président du jury CPPM

Lorenzo FELIGIONI Directeur de thèse CPPM

Mossadek TALBY Codirecteur de thèse CPPM

 

Resumé

 

The discovery of the Higgs Boson, the last particle predicted by the Standard Model (SM) of particle physics, at the Large Hadronic Collider (LHC) by the ATLAS and CMS collaborations in 2012, is a turning-point for the history of physics. The presence of a new neutral boson, with a mass of approximately 125 GeV, constrains at a different level all theoretical models providing a mechanism for spontaneous Electroweak Symmetry Breaking (EWSB) via a natural extension to the SM.  For this, the top quark, the heaviest SM fermion, plays a crucial role as it presents the largest coupling to the Higgs boson. This can be tested at tree level at the LHC via the measurement of the cross section for the Higgs and top anti-top quark pairs associated production (ttH). The focus of the work presented in this thesis, carried out within the ATLAS group at CPPM, consists of the search for ttH(H->bb) in the all-hadronic channel using Run 2 data. Among the several improvements with respect to the Run 1 version of the analysis, the most relevant is the new event selection  based on trigger level identification of b-quark initiated jets (b-tagging). In order to use b-tagging at trigger level, a calibration based on a high purity b-jet sample extracted in top anti-top events has been performed as part of the thesis work. Once made available to the whole collaboration, this calibration is now a standard for all SM, Higgs and BSM analysis that use of this class of triggers.