Study of Double Charm B Decays with the LHCb Experiment at CERN and Track Reconstruction for the LHCb Upgrade (Springer Theses)

This book discusses the study of double charm B decays and the first observation of B0->D0D0Kst0 decay using Run I data from the LHCb experiment. It also describes in detail the upgrade for the Run III of the LHCb tracking system and the trigger and tracking strategy for the LHCb upgrade, as well as the development and performance studies of a novel standalone tracking algorithm for the scintillating fibre tracker that will be used for the LHCb upgrade. This algorithm alone allows the LHCb upgrade physics program to achieve incredibly high sensitivity to decays containing long-lived particles as final states as well as to boost the physics capabilities for the reconstruction of low momentum particles. Supervisors’ Foreword 7 Abstract 10 Acknowledgements 12 Contents 13 1 Introduction to Theory 17 1.1 A Subatomic Particle Classification 18 1.2 The Fundamental Interactions of the SM 22 1.2.1 The Strong Interaction 23 1.2.2 The Electromagnetic Interaction 25 1.2.3 The Weak Interaction 25 1.3 Symmetries and Quantum Number Conservation 27 1.4 The Electroweak Theory of Weak Interaction 28 1.5 The Higgs Boson Role in the Standard Model 33 1.6 The Flavour Structure of the Standard Model 36 1.6.1 The CKM Matrix 39 References 43 2 The LHCb Detector at the LHC 45 2.1 The Large Hadron Collider 45 2.2 The LHCb Experiment at the LHC 47 2.3 LHCb Tracking System 53 2.3.1 VErtex LOcator 54 2.3.2 LHCb Dipole Magnet 57 2.3.3 Tracker Turicensis (TT) 58 2.3.4 Inner Tracker (IT) 59 2.3.5 Outer Tracker (OT) 60 2.4 LHCb Particle Identification System 61 2.4.1 RICH Detectors 62 2.4.2 Calorimeter System 64 2.4.3 Muon Stations 66 2.4.4 Particle Identification Strategy and Performance at LHCb 67 2.4.5 LHCb Trigger System 69 2.4.6 Real Time Alignment and Calibration in Run II 75 2.4.7 LHCb Software Framework and Applications 78 References 79 3 The LHCb Upgrade 82 3.1 Physics Motivation 83 3.2 Detector Upgrade: Motivations and Plans 85 3.2.1 Tracking System Upgrade 86 3.2.2 Particle Identification System Upgrade 91 3.2.3 Upgrade Readout and Online 94 3.3 Trigger for the Upgrade 95 References 99 4 Tracking in LHCb and Stand-Alone Track Reconstruction for the Scintillating Fibre Tracker at the LHCb Upgrade 100 4.1 Track Types and Tracking Strategies 101 4.1.1 Momentum Estimation Using the pT-Kick Method 103 4.1.2 VELO Tracking: PrPixelTracking 103 4.1.3 VeloUT Tracking Algorithm: PrVeloUT 105 4.1.4 Forward Tracking Algorithm: PrForwardTracking 107 4.1.5 Seeding Algorithm: PrHybridSeeding 109 4.1.6 Downstream Tracking Algorithms: PrLongLivedTracking 110 4.1.7 Matching Algorithm: PrMatchNN 111 4.1.8 Track Fit: Kalman Filter 113 4.1.9 Tracking Sequence Reconstruction for the LHCb Upgrade 117 4.1.10 Performance Indicators 119 4.2 The Scintillating Fibre Tracker Detector: Principles and Simulation 121 4.2.1 Scintillating Fibres 123 4.2.2 Silicon Photomultipliers (SiPM) 125 4.2.3 Read-Out Electronics 127 4.2.4 SciFi Simulation 129 4.3 Dedicated Track Fit in SciFi Region 136 4.3.1 Track Model 136 4.3.2 dRatio Parameterization 138 4.3.3 Track Fit Implementation 140 4.4 The Hybrid Seeding Algorithm ... 141 4.4.1 Hybrid Seeding Algorithm Overview 142 4.4.2 Find x-z Projections 144 4.4.3 x-z Projection Clone Killing 154 4.4.4 Addition of the Stereo Hits 155 4.4.5 Flag Hits on Track 166 4.4.6 Global Clone Removal Step 167 4.4.7 Track Recovery 168 4.4.8 Summary of the Changes with Respect to the TDR Seeding 170 4.4.9 Parameters Summary 171 4.5 Hybrid Seeding Performances 171 4.5.1 Results and Comparison with the TDR Seeding 171 4.5.2 Suggestions for Future Improvements 176 4.5.3 Break-Up of Algorithm Steps 180 4.5.4 Summary 183 References 183 5 The BrightarrowDDK Phenomenology 186 5.1 B Mesons Decay Modes 187 5.2 Quark Diagrams of BrightarrowD(ast)overlineD(ast)K(ast) 188 5.3 Isospin Relations 190 5.4 Hadronic Effects in B Decays 193 5.4.1 Heavy Quark Symmetry 193 5.4.2 Factorization 196 5.4.3 Color Suppression 197 5.4.4 Chiral Symmetry 198 5.5 Spectroscopy of coverlines and coverlinec States 199 5.6 B0rightarrowD0overlineD0Kast0 Role in the Charm Counting Puzzle 202 5.7 Non Resonant Components in D(ast)D(ast)Kast as Input ... 206 5.7.1 Effective Hamiltonian for brightarrows μ+ μ- and Charm Loops 207 5.8 Summary Concerning B 0 toD0overlineD 0 K *0 211 References 212 6 Measurement of the B 0 toD 0overlineD 0 K *0 Branching Ratio 214 6.1 Analysis Strategy 214 6.2 Datasets 216 6.3 Selection 217 6.3.1 Stripping 217 6.3.2 Pre-selection 219 6.3.3 Decay Tree Fitter 221 6.3.4 PID Response Resampling Using Meerkat 221 6.3.5 Multivariate Selection 222 6.3.6 Boosted Decision Trees: Overview 224 6.3.7 k-Folding of Data Samples to Maximise Statistics 228 6.3.8 Two Staged BDT Classifier 229 6.3.9 Background From Single Charmless and Double Charmless Decays 237 6.3.10 BDT Optimisation 242 6.3.11 Trigger Selection and Trigger Requirements 245 6.4 Mass Fit 250 6.4.1 Signal Yields 252 6.5 Efficiencies and Preliminary Results 254 6.5.1 Break-Down of the Various Efficiencies and Efficiency Estimation 257 6.5.2 Background Subtraction Using sPlot 258 6.6 Source of Systematics and Estimation of Kast0 Fraction in B 0 toD 0overlineD 0 K + - 266 6.7 Conclusions and Future Plans 270 References 271 Appendix Curriculum Vitae 272 Front Matter ....Pages i-xviii Introduction to Theory (Renato Quagliani)....Pages 1-28 The LHCb Detector at the LHC (Renato Quagliani)....Pages 29-65 The LHCb Upgrade (Renato Quagliani)....Pages 67-84 Tracking in LHCb and Stand-Alone Track Reconstruction for the Scintillating Fibre Tracker at the LHCb Upgrade (Renato Quagliani)....Pages 85-170 The \(B\rightarrow DDK\) Phenomenology (Renato Quagliani)....Pages 171-198 Measurement of the \(B ^0 \!\rightarrow D ^0 {\overline{D}{} ^0} K ^{*0} \) Branching Ratio (Renato Quagliani)....Pages 199-256 Back Matter ....Pages 257-262