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研究生:雷永吉
研究生(外文):Yeong-jyi Lei
論文名稱:利用緊湊渺子線圈搜尋第四世代下型夸克
論文名稱(外文):Search for a Fourth Generation Bottom-like Quark in CMS
指導教授:陳凱風
口試委員:張元翰李湘楠熊怡郭家銘張寶棣章文箴侯維恕
口試日期:2013-03-11
學位類別:博士
校院名稱:國立臺灣大學
系所名稱:物理研究所
學門:自然科學學門
學類:物理學類
論文種類:學術論文
論文出版年:2013
畢業學年度:101
語文別:英文
論文頁數:97
中文關鍵詞:高能物理新粒子
外文關鍵詞:HEPExotic Particle
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這篇論文發表了尋找新的下型夸克的結果,我們利用緊湊渺子線圈蒐 集大強子對撞機製造的7TeV質子對撞資料加以分析。
假設新型夸克b0會衰變成頂夸克以及W波色子,成對生成的新夸克有機會出現三個或兩個同電荷的帶電輕子,我們利用這個特性來辨識新型夸克。結果並沒有觀測到明顯的新物理,我們推測新夸克的質量應該 611GeV 以上,這個觀測的信心水準是95%。

Results are presented from a search for heavy bottom-like quarks, pair-produced in pp collisions at a center of mass energy of 7 TeV, undertaken with the CMS experiment at the LHC. The b0 quarks are assumed to decay exclusively to tW. The pair production process of b0 can be identified by its distinctive signatures of three leptons or two leptons of same charge, and at least one b-quark jet. Using a data
sample corresponding to an integrated luminosity of 4.9 fb
−1, observed events are compared to the standard model background predictions, and the existence of b0 quarks having masses below 611 GeV is excluded at 95% confidence level.

Chapter I Introduction 1
I.1 The Standard Model of Particle Physics 1
I.1.1 Gauge Bosons 1
I.1.2 Fermions2
I.1.3 Higgs Boson2
I.2 Beyond Standard Model: Fourth Generation of Fermions3
I.2.1 Baryogenesis and CP Violation 3
I.2.2 Neutrino Mass5
I.2.3 Electroweak Precision Data 6
I.2.4 Effect to the Higgs Boson Search 8
I.2.5 Relation with the Flavor Physics 8
I.2.6 Searchs for Fourth Generation Quarks 8
Chapter II Experiment Setup 13
II.1 The Large Hadron Collider 13
II.2 The CMS Detector 15
II.2.1 Magnet 16
II.2.2 The Tracking System16
II.2.3 The Electromagnetic Calorimeter and the Preshower Detector 17
II.2.4 The Hadron Calorimeter 18
II.2.5 The Muon System 19
II.2.6 The Trigger System 20
Chapter III ES Data Acquisition System 23
III.1 The Electronic System 23
III.1.1 The Front End Electronic System 23
III.1.2 The Off-Detector Electronic System 24
III.1.3 Data Readout and Reduction 27
III.2 The Online Software 28
III.3 Conclusion31
Chapter IV Event Reconstruction 33
IV.1 Basic Objects 33
IV.1.1 Track and Vertex Reconstruction 33
IV.1.2 ECAL Clustering 34
IV.1.3 HCAL Towering 36
IV.1.4 Standalone Muon Reconstruction 37
IV.2 The Particle-Flow Event Reconstruction 37
IV.2.1 Muon Reconstruction 37
IV.2.2 Electron Reconstruction 38
IV.2.3 Jet Reconstruction 38
IV.2.4 b-Jet Identification 40
IV.2.5 Missing Transverse Energy 40
Chapter V Strategy, Data, and Simulation 43
V.1 Analysis Strategy 43
V.2 Data Sample 44
V.3 Monte Carlo Simulation 45
V.4 Pile-up Reweighting 45
Chapter VI Selection 49
VI.1 Object Selection 49
VI.1.1 Muon Selection 49
VI.1.2 Electron Selection 50
VI.1.3 Jet and MET Reconstruction 51
VI.2 Trigger 51
VI.3 Event Selections and Event Rates 52
Chapter VII Background Estimations 63
VII.1 Type I : Single lepton events with a non prompt or fake lepton63
VII.1.1 Loose Leptons 64
VII.1.2 Fake Rates 65
VII.1.3 Control Region 66
VII.1.4 Background Yields 66
VII.2 Tpye II : Opposite-sign dilepton events with electron charge mis-tag 67
VII.2.1 Electron Charge Mis-Identification Rate67
VII.2.2 Control Region 68
VII.2.3 Background Yields 68
VII.3 Type III and Type IV: Other Events 68
Chapter VIII Estimations of Multijets Background 73
VIII.1 Control Region 73
VIII.2 Expected Yields 74
Chapter IX Systematic Uncertainties 77
IX.1 Sources of Systematic Uncertainties 77
IX.1.1 Integrated luminosity 78
IX.1.2 Trigger efficiency 78
IX.1.3 Background cross sections 78
IX.1.4 Jet energy scale78
IX.1.5 Jet energy resolution 79
IX.1.6 Missing transverse energy resolution 79
IX.1.7 Pile-up interactions80
IX.1.8 Lepton efficiency 80
IX.1.9 Parton distribution function (PDF) 80
IX.1.10 b-tagging efficiency 81
IX.1.11 Method error 81
IX.1.12 Control region statistics 81
IX.1.13 MC statistics 81
IX.2 Uncertainty on Efficiency 82
IX.3 Uncertainty on NB 82
Chapter X Result 85
X.1 Signal Region 85
X.2 Limit on b0 Mass 86
Chapter XI Conclusion 89
Bibliography 91


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