The Frontier of Modern Calorimetry: Hardware
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THE FRONTIER OF MODERN CALORIMETRY: HARDWARE ADVANCES AND APPLICATION IN PARTICLE PHYSICS ANALYSIS TATIANA MEDVEDEVA ADISSERTATION PRESENTED TO THE FACULTY OF PRINCETON UNIVERSITY IN CANDIDACY FOR THE DEGREE OF DOCTOR OF PHILOSOPHY RECOMMENDED FOR ACCEPTANCE BY THE DEPARTMENT OF PHYSICS ADVISER: CHRISTOPHER G. TULLY SEPTEMBER 2014 c Copyright by Tatiana Medvedeva, 2014. All Rights Reserved Abstract While the last missingcomponents of the SM puzzle seem to be successfully found, particle physicists remain hungry for what might be there, beyond the cosy boundaries of the well studies elementary particle world. However, the sophisticated technique of data analysis and acute Monte Carlo simulations remain fruitless. It appears that the successful intrusion into the realm, in which we were not welcome so far, may require a very different implica- tion of effort. All those results might suggest, though banal, that we need an improvement on the hardware side. Indeed, the hadronic calorimeter of CMS is no competitor to its other state-of-art components. This obstacle in many cases significantly complicates the flow of the physics analysis. Besides, the era of high luminosity LHC operation in the offing is calling for the same. After exploration of the analysis debri with 8TeV collision data, we investigate various approaches for better calorimetry for the CMS detector. iii Acknowledgements This work would have been unthinkable without many people who supported and guided me over the years. First of all, I would like to express my deep gratitude to my advisor, Christopher Tully, for numerous things I’ve learned from him as well as for his attentive guidance through- out many years of my work in Princeton High Energy Experiment team. I am especially grateful for lifting the veil on research and development in detector technology. My further education and progress in this field would not be possible without Arjan Heering, Dmitri Konstantinov and Dragoslav-Laza Lazic. I have also learned a lot from the discussions with Christian Joram, Thomas Schneider and Miranda Van Stenis. My knowledge of accelerators and experience with beam lines would not be possible without the expertise of Per Grafstro¨m, Lau Gatignon and Ilias Efthymiopoulos. I am very grateful to Andrea Benaglia, Marco Lucchini and Kristof Pauwels for pleasant and productive col- laboration and express my deep gratitude to Etiennette Auffray and Paul Lecoq for their in- valuable insight and guidance. I was lucky to work side by side with too many outstanding physicists to list here. I am thankful to the members of the SUSY Physics Analysis Group of the CMS experiment, as I’ve learned a great deal from them. I owe my knowledge of calorimeters to many experts of the electromagnetic and hadronic calorimeter teams. The years I’ve spent at CERN I was delighted to share a pleasant and friendly atmos- there of the big Princeton office with Edmund Berry, Phil Hebda, Davide Gerbaudo, Ed- ward Laird, Paul Lujan, Michael Mooney, Xiaohang Quan, Halil Saka and Andrzej Zuran- ski. I would also like to thank Kimberly Dawidowski who was a lifesaver in so many prac- tical matters. I am grateful to the administrators of Physics Department, Jessica Heslin, iv Regina Savadge and Karen Kelly for their help with numerous issues without which this work would not have been completed. I also owe gratitude to Daniel Marlow and Pierre Piroue who were offering a helping hand in a broad spectrum of life situations. I am thank- ful to Sune Jakobsen for his readiness to discuss the broad variety of technical subjects, including my – sometimes crazy – hardware-related ideas. Finally, I would like to take advantage of an oppotunity to thank my friends for their invaluable support. In particular I am thankful to (in alphabetical order) Dmitry Chech- enev, Denis Derkach, Anastasia Dolya, Olga Driga, Viacheslav Duk, Dmitry Dylov, Maria Filippova, Nikolay Groshkov, Tatiana and Maxim Gouzevitch, Vadim Jelezniakov, Anton Karneyeu, Mikhail Kirsanov, Irina and Oleksiy Kononenko, Viktoriya Kononova, Maxim Konyushikhin, Konstantin Kravtsov, Uliana Makarova, Ekaterina Mehnert, Vasily Pestun, Olga and Yury Polyanskiy, Yaroslava Profantilova, Andrei Rachkov, Roman Rafikov, Eu- gene Sedykh, Anastasia Solodko-Magazinik and Evgeny Solodko, Roman Sorokoletov, Nikolai Yampolsky, Konstantin Zhukov. I was incredibly lucky to have them all by my side. v Contents Abstract iii Acknowledgements iv Contents vi 1 Introduction 1 1.1 Standard Model ................................ 2 1.2 Beyond the SM ................................ 5 1.2.1 Grand Unified Theories (GUT) .................... 5 1.2.2 Supersymmetry (SUSY) ....................... 7 2 Input of the HEP Studies – What Do We See? 9 2.1 Biometrics of Individual Particles ...................... 10 2.1.1 Trackers: Charge and Momentum .................. 10 2.1.2 Calorimeters ............................. 11 2.1.3 Muon Detectors ............................ 15 2.2 Collective Information ............................ 16 2.2.1 Vertexing – Back to the Origin .................... 16 2.2.2 Undetectables ............................. 17 2.2.3 Jets .................................. 17 3 The LHC experimental facility 27 3.1 The accelerator complex ........................... 27 vi 3.1.1 Proton Source – Duoplasmatron ................... 28 3.1.2 Radio-Frequency Quadrupole .................... 28 3.1.3 Linac2 ................................ 31 3.1.4 Proton Synchrotron Booster ..................... 32 3.1.5 Proton Synchrotron .......................... 34 3.1.6 Super Proton Synchrotron ...................... 36 3.1.7 The Large Hadron Collider ...................... 38 3.2 The experiments ................................ 42 3.2.1 CMS ................................. 42 3.2.2 ATLAS ................................ 42 3.2.3 LHCb ................................. 44 3.2.4 ALICE ................................ 45 3.2.5 TOTEM ................................ 46 3.2.6 LHCf ................................. 47 3.2.7 MoEDAL ............................... 47 4 The CMS experiment 48 4.1 Introduction .................................. 48 4.2 Superconducting Magnet ........................... 49 4.3 Inner tracker .................................. 50 4.4 Electromagnetic Calorimeter ......................... 51 4.5 Hadron Calorimeter .............................. 53 4.6 Muon System ................................. 56 4.7 Trigger .................................... 58 5 All hadronic SUSY search 59 5.1 Stop Pair Production – Motivation of the Search and Signature ....... 60 5.2 Datasets and Triggers ............................. 61 5.3 Identification and Reconstruction ....................... 63 5.3.1 Jet Reconstruction. ”Picky” jets ................... 63 5.3.2 B-tagging ............................... 65 vii 5.3.3 Top reconstruction .......................... 65 5.4 Main Backgrounds and Baseline Selection .................. 66 5.5 Final Selection:Boosted Decision Tree .................... 68 5.5.1 Basics of Statistical Learningand Decision Trees .......... 68 5.5.2 Boosted Decision Tree ........................ 70 5.6 Lepton Vetos ................................. 72 5.6.1 Electrons and Muons ......................... 72 5.6.2 Tau Leptons .............................. 72 5.7 Background estimation ............................ 72 5.7.1 Top, W and Z( νν)+ jets ..................... 74 → 5.7.2 Multijets ............................... 76 5.7.3 ttZ .................................. 78 5.7.4 Top and W: Hybrid Monte Carlo ................... 79 5.8 Results ..................................... 81 6 Beam Lines at CERN 86 6.1 East Experimental Area ............................ 87 6.2 North Experimental Area ........................... 87 6.2.1 Beam Preparation and Slow Extraction for the North Area ..... 88 6.2.2 Beam Transfer and Primary Targets ................. 90 6.2.3 SPS page-1 .............................. 93 6.2.4 Multipurpose Wobbling Station ................... 95 6.2.5 Beam line Equipment ......................... 97 6.2.6 Control of the Particle Type in the Beam ...............104 6.2.7 Beam File Creation from Scratch ..................105 7 Crystal Fibers 114 7.1 Beam Tests in 2012 ..............................115 7.2 Geometry of the Module ...........................116 7.3 Read Out electronics and Data Acquisition system ..............117 7.4 Wire Chambers ................................118 viii 7.5 Response of Ce-Doped and Undoped LuAG Fibers .............120 7.6 Transverse Granularity ............................122 7.7 Energy Reconstruction ............................123 7.8 Longitudinal Shower Profile .........................125 7.9 Summary and Discussion of Results .....................127 7.10 Perspectives and Outlook ...........................130 7.11 Conclusions ..................................132 8 Quartz capillaries 133 8.1 Light Emitting Cores .............................134 8.2 Primary Tasks for the Bench Tests ......................135 8.3 Laboratory Setup ...............................137 8.4 Test of wavelength shifting Y11 cores ....................138 8.5 Tests of Liquid Scintillating EJ-309 Core ..................139 8.6 Double-Sided Readout for SCSF-81MJ Scintillating Core ..........140 8.7 Radiation Damage Studies of Y11 Core ...................141 8.8 Beam Tests in 2012 ..............................144 8.8.1 Geometry of the Module and DAQ ..................145 8.8.2 Pulse Shapes and Signal-Pedestal Separation ............147 8.9 Perspectives and Outlook ...........................150