First Measurement of the Running of the Top Quark Mass (Springer Theses)

In this thesis, the first measurement of the running of the top quark mass is presented. This is a fundamental quantum effect that had never been studied before. Any deviation from the expected behaviour can be interpreted as a hint of the presence of physics beyond the Standard Model. All relevant aspects of the analysis are extensively described and documented. This thesis also describes a simultaneous measurement of the inclusive top quark-antiquark production cross section and the top quark mass in the simulation. The measured cross section is also used to precisely determine the values of the top quark mass and the strong coupling constant by comparing to state-of-the-art theoretical predictions. All the theoretical and experimental aspects relevant to the results presented in this thesis are discussed in the initial chapters in a concise but complete way, which makes the material accessible to a wider audience. Supervisor’s Foreword Abstract Publications related to this thesis Acknowledgements Contents 1 Introduction References 2 The Standard Model of Particle Physics and the Top Quark 2.1 The Standard Model of Particle Physics 2.2 The Unified Theory of Electroweak Interactions 2.3 The Higgs Mechanism and Quark Mixing 2.4 Quantum Chromodynamics and Renormalization 2.5 QCD Factorization and the Evolution of Parton Distribution Functions 2.6 Monte Carlo Simulation 2.7 The Top Quark 2.8 Fixed Order Calculations for tbart Production 2.9 Simulation of tbart Events References 3 The LHC and the CMS Detector 3.1 The Large Hadron Collider 3.2 The Compact Muon Solenoid 3.2.1 The Coordinate System 3.2.2 The Tracking System 3.2.3 The Electromagnetic Calorimeter 3.2.4 The Hadron Calorimeter 3.2.5 The Muon System 3.3 The CMS Trigger System 3.4 Measurement of the Integrated Luminosity References 4 Event Reconstruction in CMS 4.1 Reconstruction of Tracks and Vertices 4.2 The Particle-Flow Algorithm 4.3 Jet Clustering and Calibration 4.4 Identification of Jets Originating from b Quarks 4.5 Identification of b Jets at the High Level Trigger 4.6 Commissioning of the Double-b Tagger References 5 Simultaneous Measurement of the Top Quark Pair Production Cross Section and the Top Quark Mass 5.1 Measuring the Top Quark Pair Production Cross Section 5.2 Data Set, Event Selection, and Monte Carlo Simulation 5.3 Systematic Uncertainties 5.4 The Fit Procedure 5.5 Extrapolation to the Full Phase Space 5.6 Results 5.7 Impact of Statistical Uncertainties in the MC Simulation References 6 Extraction of the Top Quark Mass and the Strong Coupling Constant 6.1 The QCD Analysis 6.2 Theoretical Predictions 6.3 Extraction of the Strong Coupling Constant 6.4 Extraction of the Top Quark Mass References 7 Measurement of the Running of the Top Quark Mass 7.1 Analysis Strategy 7.2 Measurement of the Differential Cross Section 7.3 Extraction of the Running References 8 Summary and Conclusions References Appendix A Impact of the Modelling Uncertainties on the Fit Distributions Appendix B Closure Test of the Simultaneous Fit of σtbart and mtMC Appendix C Cross-Check Fit of mtMC with a Single Distribution Appendix D Impact of MC Statistical Fluctuations on the Pulls and Constraints of the Modelling Uncertainties Appendix E Cross-Check Measurement of the Differential tbart Cross Section with the Loose Kinematic Reconstruction Reference