Measurement of the Z boson cross-section in - Harvard University ...

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Contents Title Page . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii 1 Introduction and Theoretical Overview 1 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 The Standard Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2.1 The Higgs mechanism . . . . . . . . . . . . . . . . . . . . . . 6 1.3 Proton-proton collisions and Z boson production at the LHC . . . . . 8 1.3.1 Internal structure of a proton and parton distributions functions 8 1.3.2 Renormalization of the strong coupling . . . . . . . . . . . . . 11 1.3.3 QCD hard scattering and factorization . . . . . . . . . . . . . 12 1.3.4 Hadronization . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.4 Z boson production at the LHC . . . . . . . . . . . . . . . . . . . . . 16 1.5 Current state of theoretical calculation of the Z cross-section . . . . . 19 1.5.1 Sources of theoretical errors . . . . . . . . . . . . . . . . . . . 22 1.5.2 Current status of PDFs . . . . . . . . . . . . . . . . . . . . . . 26 1.5.3 PDF measurements in ATLAS . . . . . . . . . . . . . . . . . . 28 1.5.4 Overall theoretical error in Z cross-section and acceptance . . 31 1.5.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2 The Accelerator and the Experiment 34 2.1 The Large Hadron Collider . . . . . . . . . . . . . . . . . . . . . . . . 34 2.2 A Toroidal LHC Apparatus (ATLAS) . . . . . . . . . . . . . . . . . . 36 2.2.1 The magnet system . . . . . . . . . . . . . . . . . . . . . . . . 38 2.2.2 The Inner Detector (ID) . . . . . . . . . . . . . . . . . . . . . 41 The Pixel Detector . . . . . . . . . . . . . . . . . . . . . . . . 41 The Semiconductor Detector (SCT) . . . . . . . . . . . . . . . 43 The Transition Radiation Tracker (TRT) . . . . . . . . . . . . 43 iv
Contents v 2.2.3 The Calorimetry . . . . . . . . . . . . . . . . . . . . . . . . . 45 The Liquid Argon (LAr) Electromagnetic Calorimeter . . . . . 45 The Hadronic Calorimeter . . . . . . . . . . . . . . . . . . . . 49 The Liquid Argon Forward Calorimeter . . . . . . . . . . . . . 50 2.2.4 The Muon Spectrometer . . . . . . . . . . . . . . . . . . . . . 51 Precision measurement technologies . . . . . . . . . . . . . . . 53 Trigger technologies . . . . . . . . . . . . . . . . . . . . . . . . 55 Magnetic field in the muon system . . . . . . . . . . . . . . . 60 Alignment of muon chambers . . . . . . . . . . . . . . . . . . 61 2.2.5 Trigger and Data Acquisition System (TDAQ) . . . . . . . . . 62 3 Luminosity Measurement at the LHC and in ATLAS 66 3.1 Luminosity measurement using beam parameters . . . . . . . . . . . 67 3.1.1 Crossing angle . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 3.1.2 Offset beams with finite crossing angle . . . . . . . . . . . . . 70 3.1.3 Hourglass effect . . . . . . . . . . . . . . . . . . . . . . . . . . 71 3.2 Determination of beam parameters relevant to luminosity measurement 72 3.2.1 Beam current measurement at the LHC . . . . . . . . . . . . . 72 3.2.2 Beam size measurement using Van der Meer scans . . . . . . . 75 3.2.3 Beam profile measurement . . . . . . . . . . . . . . . . . . . . 76 3.2.4 Beam position monitors . . . . . . . . . . . . . . . . . . . . . 80 3.2.5 The BRAN detectors for relative luminosity measurement . . 82 3.3 Luminosity monitoring in ATLAS . . . . . . . . . . . . . . . . . . . . 83 3.3.1 ALFA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 3.3.2 LUCID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 3.3.3 BCM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 3.3.4 Offline relative luminosity monitoring in ATLAS . . . . . . . . 91 3.3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 4 Data Collection and Event Reconstruction 94 4.1 Data Collection and Integrated Luminosity . . . . . . . . . . . . . . . 94 4.2 Event Reconstruction in ATLAS . . . . . . . . . . . . . . . . . . . . . 95 4.2.1 Reconstruction in the Inner Detector . . . . . . . . . . . . . . 97 Inside-out track reconstruction . . . . . . . . . . . . . . . . . . 98 Outside-in track reconstruction . . . . . . . . . . . . . . . . . 100 TRT-only track reconstruction . . . . . . . . . . . . . . . . . . 100 Vertex reconstruction . . . . . . . . . . . . . . . . . . . . . . . 101 Reconstruction of photon conversions . . . . . . . . . . . . . . 105 Beamline reconstruction . . . . . . . . . . . . . . . . . . . . . 106 Electron reconstruction in the inner detector . . . . . . . . . . 109 4.2.2 Reconstruction in the Calorimeters . . . . . . . . . . . . . . . 111 Jet reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . 114
Page 1: Measurement of the Z boson cross-se
Page 6 and 7: Contents vi Electron reconstruction
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Page 14 and 15: Acknowledgments xiv mate Niels van
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Chapter 6 Event Selection After eve
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Appendix A: Event list 245 Candidat
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Appendix A: Event list 247 Candidat
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Appendix B: Comparison of muon curv
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Bibliography 251 [13] S. Ask. Statu
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Bibliography 253 [44] S. Frixione,
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Bibliography 255 [75] N. E. Adam an
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Bibliography 257 [102] The TOTEM Co
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