Search for New Physics in tt ̅ Final States with Additional Heavy-Flavor Jets with the ATLAS Detector

Javier Montejo Berlingen

• Publisher: Springer
• Year: 2016
• Print ISBN:
  9783319410500
• eBook ISBN:
  9783319410517
• Topic: Physical Sciences
• Subtopic: Quantum Theory

This doctoral thesis focuses on the search for new phenomena in top-antitop quark (tt) final states with additional b-quark jets at the LHC. It uses the full Run 1 dataset collected by the ATLAS experiment in proton-proton collisions at ?s=8 TeV. The final state of interest consists of an isolated lepton, a neutrino and at least six jets with at least four b-tagged jets, a challenging experimental signature owing to the large background from tt+heavy-flavor production. This final state is characteristic of ttH production, with the Higgs boson decaying into bb, a process that allows direct probing of the top-Higgs Yukawa coupling. This signature is also present in many extensions of the Standard Model that have been proposed as solutions to the hierarchy problem, such as supersymmetry or composite Higgs models, which predict the pair production of bosonic or fermionic top quark partners, or the anomalous production of four-top-quark events. All these physics processes have been searched for using an ambitious search strategy that has been developed on the basis of a combination of state-of-art theoretical predictions and a sophisticated statistical analysis to constrain in-situ the large background uncertainties. As a result, the most restrictive bounds to date on the above physics processes have been obtained.

Table of contents

• Supervisor’s Foreword
• Publications related to this thesis:
• Contents
• Preamble
• 1 Introduction and Theoretical Framework
• 2 The ATLAS Experiment at the Large Hadron Collider
• 3 Event Simulation
• 4 Reconstruction of Physics Objects
• 5 Common Aspects in Searches for New Physics in tbart Final States with Additional Heavy-Flavor Jets
• 6 Statistical Analysis
• 7 Searches for New Physics in tbart Final States with Additional Heavy-Flavor Jets
• 8 Conclusions
• Appendix ATiming Performance of the Tile Calorimeterwith Muons from Collision Data
• Appendix Bt ¯t + HF Modeling
• Appendix CInput Variables to the Neural Networkin the t ¯tH Analysis
• Appendix DPost-fit Distributions for Kinematic Variables
• Appendix EGlossary