Top-quark background estimation for physics BSM in the di-lepton and jets final state with the ATLAS detector

Abstract

This thesis presents the top-quark background estimation for the search of a heavy scalar, H, that decays into the Standard Model Higgs boson and a Higgs-like scalar, S. This model is an extension of the Standard Model, where the S and H interact with the Standard Model Higgs boson. This work uses the dataset corresponding to an integrated luminosity of 36 fb−1 of pp collisions at a center-of-mass energy of √s=13 TeV collected by the ATLAS detector. The final state considered for this analysis is composed of two oppositely charged leptons with different flavour (e±μ∓) and jets. The dominant Standard Model background in this search is the top-quark processes (tt and Wt). Top quark control and validation regions are defined and studied. The validation region is used to test the MC modeling of the top quark processes in regards to leptonic kinemates. In this region, data-driven corrections have been extracted to improve Monte Carlo modeling. Higher order electroweak corrections are implemented in the Monte Carlo simulation to improve t ̄t modeling. The derived normalization factor in the top-quark control region is applied to the top-quark processes in both the control and the signal regions