Development of a new tracker for the CMS upgrade phase 2 and study of the HL-LHC physics reach

This thesis explores the upgrade of the CMS silicon strip detector, centred around the in-beam characterisation of detector module prototypes and discusses the physics reach of the upgraded machine, with an emphasis on Higgs boson pair production in the bbWW(l) final state. Read More

The standard model of particle physics provides a coherent description of highenergy physics processes and has been hugely successful in providing experimental predictions. Among its long list of achievements, the most significant is arguably that of the discovery of the Higgs boson half a century after being theorised, providing the last cornerstone needed for the standard model to become fully consistent. Despite huge successes, the standard model still suffers from major shortcomings. On the path leading towards a better understanding of particle physics, an in-depth study of the Higgs boson is key.
This relentless work of characterising the properties of the Higgs boson is currently being undertaken at the Large Hadron Collider, where high-energy proton collisions are being recorded by dedicated detectors, providing a continuous improvement to the understanding of the standard model. Amid tremendous achievements, some processes, remain too weak to be detected with the current installations. One such measurement is the combined production of two Higgs bosons allowing for a direct handle on the Higgs self-coupling parameter of the standard model.
To maximise the physics reach of the collider, it will be subjected to a major upgrade, allowing for a strong increase in luminosity. Such a dramatic change will bring major challenges to the experiments recording these collisions and upgrades are required if they are to maintain their outstanding performance.
This thesis explores the upgrade of the CMS silicon strip detector, centred around the in-beam characterisation of detector module prototypes and discusses the physics reach of the upgraded machine, with an emphasis on Higgs boson pair production in the bbWW(l) final state.


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Specifications


Publisher
Presses universitaires de Louvain
Author
Martin Delcourt,
Set
Language
English
BISAC Subject Heading
SCI055000 SCIENCE / Physics > SCI074000 SCIENCE / Physics / Atomic & Molecular
BIC subject category (UK)
PH Physics > PHM Atomic & molecular physics
Onix Audience Codes
06 Professional and scholarly
CLIL (Version 2013-2019)
3058 Physique
Title First Published
26 November 2020
Subject Scheme Identifier Code
: Physique atomique et moléculaire
: Physique

Paperback


Publication Date
26 November 2020
ISBN-13
9782390610052
Extent
Main content page count : 170
Code
101078
Dimensions
16 x 24 cm
Weight
281 grams
Packaging Type
No outer packaging
List Price
40.00 €
ONIX XML
Version 2.1, Version 3

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Contents


Introduction 9
1 The standard model of particle physics 11
1.1 Fundamental particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.2 Standard model Lagrangian . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.3 Predictions in particle physics . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.4 Issues in the standard model . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2 Experimental high energy physics with the CMS detector 23
2.1 CERN and the Large Hadron Collider . . . . . . . . . . . . . . . . . . . . 23
2.1.1 The LHC injectors . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.1.2 The Large Hadron Collider . . . . . . . . . . . . . . . . . . . . . . 26
2.1.3 Luminosity and pile-up . . . . . . . . . . . . . . . . . . . . . . . . 27
2.2 The Compact Muon Solenoid experiment . . . . . . . . . . . . . . . . . . 29
2.2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.2.2 The silicon tracker . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.2.2.1 The pixel detector . . . . . . . . . . . . . . . . . . . . . . 32
2.2.2.2 The silicon strip tracker . . . . . . . . . . . . . . . . . . . 33
2.2.3 The electromagnetic calorimeters . . . . . . . . . . . . . . . . . . . 36
2.2.4 The hadronic calorimeters . . . . . . . . . . . . . . . . . . . . . . . 37
2.2.5 The muon chambers . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.2.6 Trigger and data acquisition systems . . . . . . . . . . . . . . . . . 41
2.2.6.1 Level-1 trigger . . . . . . . . . . . . . . . . . . . . . . . . 41
2.2.6.2 Data acquisition and High-Level trigger . . . . . . . . . 43
2.3 Data reconstruction and enhancement techniques . . . . . . . . . . . . . 45
2.3.1 Object reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . 45
2.3.1.1 Tracking and calorimetry . . . . . . . . . . . . . . . . . . 45
2.3.1.2 Muon reconstruction . . . . . . . . . . . . . . . . . . . . 48
2.3.1.3 Electron and Photon reconstruction . . . . . . . . . . . . 49
2.3.1.4 Jet reconstruction . . . . . . . . . . . . . . . . . . . . . . 50
2.3.1.5 Missing transverse energy . . . . . . . . . . . . . . . . . 52
2.3.2 Analysis strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
2.3.2.1 Detector simulation . . . . . . . . . . . . . . . . . . . . . 54
2.3.2.2 Data enhancement . . . . . . . . . . . . . . . . . . . . . . 55
2.3.2.3 Statistical analysis . . . . . . . . . . . . . . . . . . . . . . 58
2.4 Higgs boson pair production measurements . . . . . . . . . . . . . . . . 60
3 The CMS experiment at the HL-LHC 63
3.1 The High-Luminosity LHC . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.2 The CMS upgrade for the HL-LHC . . . . . . . . . . . . . . . . . . . . . . 65
3.2.1 Trigger and data acquisition . . . . . . . . . . . . . . . . . . . . . . 65
3.2.2 The Silicon tracker upgrade . . . . . . . . . . . . . . . . . . . . . . 67
3.2.2.1 Inner Tracker . . . . . . . . . . . . . . . . . . . . . . . . . 67
3.2.2.2 Outer Tracker . . . . . . . . . . . . . . . . . . . . . . . . . 68
3.2.2.3 Layout and expected performance . . . . . . . . . . . . . 69
3.2.2.4 Trigger primitives . . . . . . . . . . . . . . . . . . . . . . 70
3.2.3 The MIP timing detector . . . . . . . . . . . . . . . . . . . . . . . . 73
3.2.4 Upgrade of the ECAL barrel . . . . . . . . . . . . . . . . . . . . . . 74
3.2.5 Upgrade of the HCAL barrel . . . . . . . . . . . . . . . . . . . . . 76
3.2.6 The high granularity calorimeter endcaps . . . . . . . . . . . . . . 76
3.2.7 Upgrade of the muon detectors . . . . . . . . . . . . . . . . . . . . 79
3.2.7.1 Upgrade of the existing muon detectors . . . . . . . . . 79
3.2.7.2 Improving muon measurements in the very forward region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
3.2.8 Summary of the CMS upgrade for the HL-LHC . . . . . . . . . . 82
4 Characterization of the cms binary chips and their read-out systems 85
4.1 CBC2 design and test campaign . . . . . . . . . . . . . . . . . . . . . . . . 85
4.1.1 2S modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.1.2 The CMS Binary Chip v2 . . . . . . . . . . . . . . . . . . . . . . . 87
4.1.3 A typical test beam setup . . . . . . . . . . . . . . . . . . . . . . . 89
4.1.4 Calibrating and characterising a module . . . . . . . . . . . . . . 91
4.1.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
4.1.6 The Louvain low energy proton beam test . . . . . . . . . . . . . . 98
4.2 CBC3 design and test campaign . . . . . . . . . . . . . . . . . . . . . . . . 104
4.2.1 Changes with respect to version 2 . . . . . . . . . . . . . . . . . . 104
4.2.2 CBC3 mini-module beam test . . . . . . . . . . . . . . . . . . . . . 105
4.3 Towards the final detector . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
5 Double Higgs discovery opportunities at the HL-LHC 111
5.1 Higgs boson pair production at the HL-LHC . . . . . . . . . . . . . . . . 111
5.1.1 Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
5.1.2 Systematic uncertainties . . . . . . . . . . . . . . . . . . . . . . . . 113
5.2 HH→bbbb channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
5.3 HH→bbττ channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
5.4 HH→bbγγ channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
5.5 HH→bbZZ channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
5.6 HH→bbWW channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5.6.2 Signal samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
5.6.3 Event selection and background predictions . . . . . . . . . . . . 124
5.6.4 Signal extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
5.6.5 Systematic uncertainties . . . . . . . . . . . . . . . . . . . . . . . . 132
5.6.6 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
5.7 Combination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
5.8 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
Conclusion 140
Appendix 141
A Beam test read-out chain 141
A.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
A.2 Data formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
A.2.1 Cbc output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
A.2.2 SLink data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
A.2.3 Offline data formats . . . . . . . . . . . . . . . . . . . . . . . . . . 148
B Louvain beam test 151
Acronyms 155
References 159