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Property Measurements of the Higgs Boson and Search for High Mass Resonances in Four-Lepton Final State with the ATLAS Detector at the LHC

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Property Measurements of the Higgs Boson and Search for High Mass Resonances in Four-Lepton Final State with the ATLAS Detector at the LHC Property Measurements of the Higgs Boson and Search for High Mass Resonances in Four-Lepton Final State with the ATLAS Detector at the LHC by Nan Lu A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Physics) in The University of Michigan 2017 Doctoral Committee: Professor Bing Zhou, Chair Professor Finn Larsen Professor Homer A. Neal Professor Gregory Tarle Professor Ji Zhu Nan Lu [email protected] ORCID iD: 0000-0002-2631-6770 c Copyright by Nan Lu 2017 All Rights Reserved ACKNOWLEDGEMENTS First and foremost, I would like to express my deepest gratitude to my advisor Bing Zhou for her guidance and support though my Ph.D. study. Bing's vision, leadership, dedication and immense knowledge have deeply influenced me. I am extremely fortunate to have Bing as my advisor. Besides my advisor, I would like to thank other members of my thesis committee: Finn Larsen, Homer A. Neal, Gregory Tarle and Ji Zhu, for reviewing my thesis and providing very helpful and enlightening comments. I am very grateful for the opportunities to take the physics courses offered by Myron Campbell, Henriette Elvang, Emanuel Gull, Gordon L. Kane, David Luben- sky, Roberto D. Merlin, Leonard M. Sander, and Bing Zhou, which have helped me appreciate the beauty of physics and have laid the foundations for my research work. I would like to express my sincere gratitude to the Michigan ATLAS group. I thank Haijun Yang for teaching me the concepts and methods in physics analysis during my early time in the group. My thanks to Lailin Xu for helping me learn physics analysis software and the nice collaboration on several research projects. I appreciate his patience to help and discuss with me at all times. My thanks also go to Cong Geng for developing the very nice analysis framework for the event selection in Run 2 and the pleasant collaboration on the HZZ physics analyses. I also thank Yusheng Wu for the illuminating discussions in many aspects of the physics analyses that I have worked on and his advice on career developments. I would like to thank Dante Amidei, Homer A. Neal, Jianming Qian, Tom Schwarz, Junjie Zhu for the insightful discussions on physics analyses and encouragements to me. I sincerely thank Tiesheng Dai for training and supervising me on the hardware work projects including the New Small Wheel simulation study for the L1 trigger and debugging the 12.5 ns T0 time jump issue in the MDT readout electronics, which are crucial learning and research experiences to me. I also thank John Chapman and Bob Ball for their help in debugging the 12.5 ns T0 time jump issue. I would like to thank Shawn McKee, Bob Ball, and Benjeman Meekhof for their strong support of computing resources, which is an indispensable asset to my research projects. I also thank other former ii and present colleagues in the Michigan group: Tom Cheng, Edward Diehl, Haolu Feng, Philipp Fleischmann, Liang Guan, Wen Guo, Yicheng Guo, Bing Li, Xuefei Li, Hao Liu, Jianbei Liu, Lulu Liu, Yanlin Liu, Daniel Marley, Allison McCarn, Karishma Sekhon, Ismet Siral, Rongkun Wang, Aaron White, Zhaoxu Xi, Jiaming Yu, Dongliang Zhang, and many others for their friendship and help. I am very fortunate to have the opportunities to work with many outstanding physicists as a member of the ATLAS Collaboration. I would like to express my sincere gratitude to Hong Ma and Eleni Mountricha from Brookhaven National Laboratory for the successful and pleasant collaboration on the physics analyses in the HZZ sub- working group. I am deeply grateful to Hong Ma for his guidance and encouragement to me. My special thanks to Eleni for all the support, encouragement and guidance which have made a difference in my research. I am very grateful for the opportunity to closely work with you over the past two years, and it has been a wonderful experience for me. I sincerely thank Fabio Cerutti for his help and support to me in the combined Higgs boson spin and parity study in diboson channels and Higgs boson coupling measurements in the four-lepton final state. I have learned a lot from his sharp insight in physics. I would also like to express my sincere gratitude to Stefano Rosati. Under his help and support, I started to learn how to perform combined measurements of the Higgs boson properties. I am also very grateful for his guidance and enlightening discussions with me on the Higgs boson property measurements in the four-lepton final state for Run 2. I am very thankful to Bruno Mansoulie for the support in several physics analyses that I have worked on. His insightful comments and discussions have been very helpful to me. I appreciate very much the enriching experience working with colleagues in the HZZ sub-working group on the high mass search and Higgs coupling measurements in the four-lepton final state. I am very grateful for the guidance and support from the HZZ conveners Rosy Nicolaidou, Robert Harrington, Roberto Di Nardo, Sarah Heim, Eleni Mountricha and Arthur Schaffer. I also thank Haider Abidi, Gaetano Barone, Valerio Bortolotto, Graham Cree, Denys Denysiuk, Tulay Donszelmann, Katharina Ecker, Andrea Gabrielli, Cong Geng, Wen Guo, Xiangyang Ju, Maria Hoffmann, Gi- ada Mancini, Jochen Meyer, Ioannis Nomidis, Hideki Okawa, Lars Pedersen, Antonio Salvucci, Monica Trovatelli, David Valentino, Rongkun Wang, Yusheng Wu, Lailin Xu, and many other colleagues. It has been a great pleasure working with you. iii I would like to thank colleagues working on the combined measurement of Higgs boson production and decay rates. I appreciate very much the coordination and support from the Higgs working group conveners Fabio Cerutti, Michael Duehrssen and Bruno Mansoulie, the Hcomb sub-working group conveners Nicolas Berger, Eric Feng, and Elisabetta Pianori. I also thank Lydia Brenner, Carsten Burgard, Xiaohu Sun and Jared Vasquez for the great teamwork. I have learned a lot from all of you. I would like to thank colleagues working on the Higgs boson spin and parity study in the four-lepton channel and in combining the diboson channels. I appreciate very much the coordination and support from the Higgs working group conveners Marumi Kado and Pierre Savard, the Hcomb sub-working group conveners Bruno Mansoulie and Kirill Prokofiev. I thank the Editorial Boards chaired by Karl Jakobs and Alean- dro Nisati for the very helpful discussions. I am grateful for the guidance and support from Fabio Cerutti, Kirill Prokofiev, and Stefano Rosati. I also thank Valerio Bor- tolotto, Eric Feng, Katharina Ecker, Tulay Donszelmann, Andrea Gabrielli, Haonan Lu, Lars Pedersen, Antonio Salvucci, Lailin Xu for their help. My sincere thanks also go to Bing Li, Xuefei Li, Jianbei Liu and Lailin Xu for their help and guidance to me in the Z 4` analysis. For the inclusive four-lepton analysis, ! I would like to thank Bing Li and Yusheng Wu for the support and discussions. In the vvqq diboson resonance search, I thank Yicheng Guo, Francesco Lo Sterzo, Chao Wang and Lailin Xu for their help. I would like to thank Elise Bodei, Joseph Sheldon, Paul Thurmond and Christina Zigulis for the outstanding administrative support. My special thanks to Christina for her kind help as the graduate program coordinator. Especially during the years when I was based at CERN, her remote help meant a lot to me. Finally, I would like to express my sincere gratitude to my parents, my grandpar- ents, and my husband Hongtao Yang. I am deeply grateful for your unconditional love and supporting my pursuit of experimental particle physics. This thesis is dedicated to you. iv TABLE OF CONTENTS ACKNOWLEDGEMENTS :::::::::::::::::::::::::: ii LIST OF FIGURES ::::::::::::::::::::::::::::::: viii LIST OF TABLES :::::::::::::::::::::::::::::::: xv ABSTRACT ::::::::::::::::::::::::::::::::::: xviii CHAPTER I. Introduction ..............................1 II. Theory ..................................4 2.1 The Standard Model of Particle Physics............4 2.1.1 The Lagrangian of the Standard Model.......6 2.1.2 The Higgs Mechanism.................9 2.1.3 Natural Unit...................... 12 2.2 Higgs Boson Phenomenology at the LHC........... 13 2.2.1 Phenomenology of Proton-Proton Collisions..... 13 2.2.2 SM Higgs Boson Production at the LHC...... 15 2.2.3 SM Higgs Boson Decays............... 16 2.2.4 Beyond the Standard Model............. 18 III. The Large Hadron Collider and the ATLAS Experiment ... 25 3.1 The Large Hadron Collider................... 25 3.1.1 Introduction...................... 25 3.1.2 Luminosity....................... 26 3.2 The ATLAS detector...................... 29 3.2.1 Inner Dectector.................... 29 3.2.2 Calorimeters...................... 33 3.2.3 Muon Spectrometer.................. 34 3.2.4 Trigger......................... 37 v 3.2.5 Data Collection.................... 42 IV. ATLAS Event Reconstruction ................... 44 4.1 Tracking............................. 44 4.1.1 Tracking in Inner Detector.............. 44 4.1.2 Tracking in Muon Spectrometer........... 45 4.2 Primary Vertex.......................... 46 4.3 Electron.............................. 46 4.3.1 Electron Reconstruction............... 46 4.3.2 Electron Identification................ 47 4.3.3 Electron Isolation................... 47 4.4 Muon............................... 48 4.4.1 Muon Reconstruction................. 48 4.4.2 Muon Identification.................. 49 4.4.3 Muon Isolation..................... 50 4.5 Jet................................. 50 4.5.1 B-Jet Tagging..................... 50 V. H ZZ∗ 4` Event Selection ................... 52 ! ! 5.1 Trigger.............................. 52 5.2 Object Selection......................... 53 5.3 Four-Lepton Selecton...................... 54 5.4 Mass Resolution in the H ZZ∗ 4` Detection....... 55 5.5 Background Estimation.....................! ! 56 5.6 Expected and Observed Events................. 57 5.7 Event Display.......................... 57 VI. Statistical Method ........................... 64 6.1 Statistical Modeling....................... 64 6.1.1 Parameterization................... 64 6.1.2 Likelihood Construction................ 65 6.2 Statistical Approach....................... 67 6.2.1 Profile Likelihood Ratio................ 68 6.2.2 Ratio of Profiled Likelihoods............
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