Searches for beyond the standard model physics in dijet resonances and development of a new b-tagging calibration algorithm at the ATLAS experiment at CERN

Abstract

This Ph.D. dissertation describes the development of a new b-tagging calibration algorithm which helps to correctly identify jets originated from b quarks at the ATLAS detector at European Organization for Nuclear Research (CERN). B-tagging has been crucial for physics programs at the ATLAS experiment and the newly developed technique aims to improve its performance.

The dissertation also addresses the R&D efforts for the upgrade of Internal Tracker (ITk) of the ATLAS detector for the upcoming High-Luminosity LHC.

Finally, the dissertation presents a search for dijet resonances in events with identified leptons, which has been performed using data collected in proton-proton collisions at square root of s=13 TeV by the ATLAS experiment at CERN between 2015 and 2018, corresponding to an integrated luminosity of 139 fb^-1. The study investigated the possibilities of new physics beyond the standard model in the dijet invariant mass distributions in the range of 0.22<mjj<6.3 TeV. The analysis probes much lower mjj than traditional inclusive dijet searches and is sensitive to a wide range of new physics models with a final-state lepton. This dissertation summarizes the results of interpretation of dijet resonance search in terms of Charged Higgs boson decaying into top and bottom quarks. The dissertation also discusses possible extensions of scopes for similar dijet resonance searches using multi-body search techniques.