Selected measurements of final states with third-generation fermions in proton – proton collisions using the ATLAS detector at the LHC

Abstract

This monograph is focused on the measurements performed by the ATLAS experiment using final states containing third-generation fermions in the recent years and covers both the Run-1 and early Run-2 data taking periods of proton – proton collisions at ps = 7, 8 and 13 TeV centre-of-mass energies. The ATLAS algorithms for reconstructing and identifying the hadronically-decaying τ leptons and hadronic jets containing b-hadrons are described in detail, covering both the end-of-Run-1 status and Run-2 developments. In addition, experimental measurements of the efficiencies of these algorithms are presented together with the results on their misidentification rates in background objects. Selected measurements (and derived conclusions) in the Standard Model sector are presented, including the measurement of τ polarisation in Z-boson decays and measurements in the SM Higgs sector with both ττ and bb final states. This is followed by a presentation of selected searches for non-Standard-Model Higgs bosons, including the heavy neutral one in di-τ and di-b decays as well as the searches for the charged Higgs boson in τυ and tb channels. No deviation from Standard-Model predictions is observed in any of the presented analyses and no hint of non-SM Higgs boson existence was found. Exclusion limits are presented instead.