博碩士論文 101222020 詳細資訊




以作者查詢圖書館館藏 以作者查詢臺灣博碩士 以作者查詢全國書目 勘誤回報 、線上人數:19 、訪客IP:3.236.156.34
姓名 張祐祥(Yu-hsiang Chang)  查詢紙本館藏   畢業系所 物理學系
論文名稱 以大型強子對撞機裡的緊湊渺子線圈偵測器尋找重夸克在半輕子頻道衰變成頂夸克和光子
(Search for pair production of a heavy quark decaying into top quark and photon in semi-leptonic channel with the CMS detector in the LHC)
相關論文
★ 7 TeV 和2.76 TeV 質子對撞下,光子散射截面積的測量★ Search for Pair Production of t*-> t + photon : Estimation of Photon Purity and Study of the Top and W Mass Resolution
★ Search for Z′→Zh→llbb in pp Collisions at √s =8 TeV Using the CMS Detector at the LHC★ Search for heavy resonances decaying into a Z boson and a Higgs boson in the 2l2b final state in pp collisions at √s = 13 TeV
★ 從質子質子對撞在質量中心能量 13 兆電子 伏特利用緊湊渺子偵測器尋找重粒子衰變 到一對希格斯粒子於四個底夸克最終態★ Study of the b-tagging Scale Factor using the tt ̅ Events from pp collisions at √s =13 TeV with the CMS Detector
★ 在大型強子對撞機的緊湊渺子線圈偵測器,使用13兆電子伏特的質子-質子對撞尋找會衰變到一對希格斯玻色子且最終狀態為四個底夸克的重共振態★ 在緊湊渺子線的質心對撞能量為 13 兆電子伏特的數據裡, 用字母法輔以突起搜尋之方法來尋找類 Z 玻色子衰變為 Z 玻色子及希格斯粒子在衰變為輕子與底垮克
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摘要(中) 我們使用CMS在2012年所蒐集的積分亮度為19.7-1 fb、LHC質子對撞質心能量為8 TeV的數據來找尋激發態頂夸克。 在我們分析中的衰變過程和最終產物是:激發態頂夸克、反激發態頂夸克->頂夸克、光子、反頂夸克、光子->底夸克、W玻色子、光子、反底夸克、W玻色子、光子,然後其中一個W玻色子以輕子的方式衰變而另一個W玻色子以夸克的方式衰變,所以我們藉著要求事件中有兩個光子、一個輕子和至少四個噴流來定義訊號區域。χ2排序法被用來重建激發態頂夸克的質量,並且從數據中有十二個事件在訊號區域被觀察到。矩陣法被用在兩個光子的頻道裡來估計這十二個事件中的背景貢獻。這個研究的結果是沒有顯著的超過預期的多餘事件被觀察到,所以對於激發態頂夸克的質量我們以95%的信心水準設了一個低限在969 GeV/c2。
摘要(英) Using the data collected by the CMS detector in 2012, corresponding to a luminosity of 19.7 / fb of proton-proton collisions at LHC center-of-mass energy of 8 TeV, we search for the excited top quark, T*. The decay process and the final states studied in our analysis are: T* T*bar -> t γ tbar γ -> b W+ γ bbar W- γ, where one W boson decays hadronically and the other leptonically, so we define a signal region by requesting events with 2 photons, 1 lepton and >= 4jets. To reconstruct the invariant mass of T*, a χ2-sorting method is used and 12 events are observed in the signal region from data. The matrix method is used to estimate the background contribution among the observed 12 events in the di-photon channel. As a result of this study, no significant excess is observed over expectations and a lower limit is set on a t* quark mass of 969 GeV/c2 at 95% confidence level.
關鍵字(中) ★ 重夸克
★ 緊湊渺子線圈
★ 大型強子對撞機
★ 頂夸克
★ 光子
關鍵字(英) ★ heavy quark
★ CMS
★ LHC
★ top quark
★ photon
論文目次 Contents
Abstract ……………………………………………………………… i
中文提要 ……………………………………………………………… ii
感謝 ……………………………………………………………… iii
Contents ……………………………………………………………… iv
List of table ……………………………………………………………… v
List of figure ……………………………………………………………… vi

Chapter 1 Introduction 1
Chapter 2 LHC and CMS detector 3
2.1 The Large Hadron Collider 3
2.2 The Compact Muon Solenoid Detector 5
2.2.1 Tracker 6
2.2.2 Electromagnetic Calorimeter 9
2.2.3 Hadronic Calorimeter 10
2.2.4 Muon Chamber 12
2.2.5 Magnet system 13
Chapter 3 CMS Trigger 14
3.1 Level-1 trigger 15
3.1.1 Muon triggers system in L1 17
3.1.2 Calorimeter triggers system in L1 17
3.1.2.1 The Electromagnetic Candidate Algorithm 19
3.1.2.2 The Jet Candidate Algorithm 21
3.1.2.3 Other calorimeter trigger tasks 23
3.1.3 Global trigger in L1 24
3.2 High Level trigger 25
3.2.1 electrons/photons 25
3.2.2 Muon 35
3.2.3 Jet 36
3.2.4 Missing transverse energy 37
3.3 The triggers used in our analysis 38
Chapter 4 Event reconstruction in offline and our event selection 39
4.1 The anti-kt jet algorithm 39
4.2 The particle flow (PF) algorithm 41
4.3 The r9 variable and the missing hits 43
4.4 The shower shape variable σiηiη 44
4.5 The isolation variables 45
4.6 The event selection in our analysis 46
Chapter 5 data and the simulated sample 51
Chapter 6 Mass Reconstruction 60
6.1 The χ2-sorting method 60
6.2 The neutrino’s pz solution 62
Chapter 7 background estimation: the matrix method 63
7.1 The introduction of matrix method 63
7.2 the photon fake rate from lepton εl 66
7.3 The photon fake rate from jet εj 68
7.4 The photon signal efficiency εs 72
7.5 The ratio factor 74
Chapter 8 Result 75
Chapter 9 Conclusion 79
Appendix A the derivation of Matrix method 80
Reference 90

List of tables
Table 3.1 the list of the objects sent from GCT to GT 18
Table 3.2 tau decay branching ratio 22
Table 3.3 global trigger menu 24
Table 3.4 parameter of hybrid algorithm 28
Table 3.5 trigger path of our analysis 38
Table 5.1 dataset of our analysis 51
Table 5.2 MC samples used in our analysis 52
Table 5.3 event yields before/after scale factors 53
Table 5.4 event yields in the loose region 59
Table 7.1 fit result of fake rate from jets 71
Table 8.1 event yields in the signal region 77

List of figures
Figure 1.1 The diagram of t* decay 2
Figure 2.1 The CERN accelerator complex 3
Figure 2.2 The main accelerator rings and their beam particles 4
Figure 2.3 The CMS detector 5
Figure 2.4 The CMS coordinate 6
Figure 2.5 The pixel detector 6
Figure 2.6 The pixel material budget 7
Figure 2.7 The layout of tracker 8
Figure 2.8 The layout of tracker 9
Figure 2.9 The layout of ECAL 10
Figure 2.10 The relative positions of ECAL and HCAL 11
Figure 2.11 The relative positions of muon chambers 13
Figure 3.1 The overview of the L1-trigger and the HLT 15
Figure 3.2 the schematic diagram of the data flow in L1-trigger 16
Figure 3.3 the L1-trigger 16
Figure 3.4 The strip, the trigger tower and the calorimeter region grouping 18
Figure 3.5 illustration of the calorimeter trigger e/γ algorithm 20
Figure 3.6 illustration of the calorimeter trigger jet algorithm 22
Figure 3.7 Illustration of the Island clustering algorithm 26
Figure 3.8 Illustration of the super-clusters 27
Figure 3.9 Domino construction step of Hybrid algorithm 27
Figure 3.10 Illustration of the crystal off-pointing and the schematic diagram 30
Figure 3.11 Distribution of Emeas/Etrue 31
Figure 3.12 Emeas/Etrue as a function of the number of crystals 32
Figure 3.13 matching the hits in pixel detector 33
Figure 4.1 anti-kt clustered jets 40
Figure 4.2 consideration of the Bremsstrahlung photon emission of electron 42
Figure 4.3 The schematic diagram of particle flow algorithm 43
Figure 4.4 Missing Hits 44
Figure 4.5 Sketch of the photon isolation 45
Figure 5.1 The number of vertices before/after applying scale factors 54
Figure 5.2 the objects’ multiplicities 55
Figure 5.3 the kinematic distributions 56
Figure 5.4 Four leading jets pT distributions 57
Figure 5.5 Jets’ pT distributions for run dependences 58
Figure 6.1 The invariant mass of a top and a photon using the χ2-sorting method 61
Figure 6.2 The t* mass spectra with different neutrino’s solutions 62
Figure 7.1 the schematic of 3 levels of the events with two photons 64
Figure 7.2 the schematic of the tight, the loose and the FO selection of photon 64
Figure 7.3 Electron-Photon invariant mass fit for the no-electron-veto selection and the tight ID selection 67
Figure 7.4 the object has a photon associated with a jet within the cone of size 0.5 68
Figure 7.5 the schematic of the NjFO and NjT 69
Figure 7.6 Results of the template fitting for the various categories 71
Figure 7.7 Muon-Muon-Photon invariant mass fit for the no-electron-veto selection and the tight ID selection 73
Figure 8.2 The mass spectrum in the signal region 76
Figure 8.3 the exclusion limit 78
Figure A-1 82
Figure A-2 83
Figure A-3 86
Figure A-4 87
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指導教授 余欣珊(Shin-Shan Yu) 審核日期 2014-7-21
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