Harish Potti
Published: 2020
Total Pages: 300
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The top quark is the heaviest known elementary particle. With a coupling to the Higgs boson close to unity, the top quark plays a special role in electroweak symmetry breaking as well as in physics beyond the Standard Model. An accurate measurement of its properties can provide key information for understanding the physics at the TeV scale. In this dissertation, two measurements of the top quark properties are presented. The first part of this dissertation presents the first-ever ATLAS search for the associated production of a single top quark and a photon. This analysis is performed with 139 fb−1 of pp collision data collected by the ATLAS detector at the LHC at [square root symbol] s = 13 TeV. Only final states with exactly one lepton and at least one photon are considered in this analysis. In the second part, results from the combination of ATLAS searches for flavor changing neutral currents (FCNC) in t->Hq decays are presented. Four FCNC analyses, probing different Higgs decay modes, performed with 36.1 fb−1 of proton-proton collision data collected by the ATLAS detector in 2015-2016 are considered in the combination. They search for top-quark pair events in which one top quark decays into Wb and the other top quark decay into Hq