Abstract
The Large Hadron Collider (LHC) is the accelerator to provide a high energy condition to generate the fundamental particles. The Higgs boson (h) predicted by the Standard Model (SM) with mass of 125 GeV was discovered through the LHC experiment in 2012. A beyond Standard Model, type-II two Higgs-doublet model (2HDM), predicts the existence of two opposite parity charge but electric neutral Higgs bosons (H / A), which are heavier than h. This study focuses on the production of the heavy Higgs boson, decayed into a pair of top quarks and associated with another pair of top quarks, i.e., tt ̅H / A→tt ̅tt ̅, in the final state of one lepton or two opposite charged leptons. The dataset is collected from an integrated luminosity of 139 fb-1 proton-proton collisions at a center-of-mass energy of 13 TeV by the ATLAS detector in the LHC. A multivariate classifier, Boosted Decision Trees (BDT), is used to separate the signal from the background. The 95% CL upper limits on the cross-section times branching ratio of H / A→tt ̅ for the heavy Higgs boson with mass of 400 GeV to 1000 GeV are estimated by certain statistical techniques.
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