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研究生:波卓洛
研究生(外文):Pocholo Luis Pasol Mendiola
論文名稱(外文):Search for H→Zγ→bbγ produced in association with a Z boson in proton-proton collisions at √s = 13 TeV with the CMS detector at the LHC
指導教授:郭家銘郭家銘引用關係
指導教授(外文):Chia-Ming, Kuo
學位類別:碩士
校院名稱:國立中央大學
系所名稱:物理學系
學門:自然科學學門
學類:物理學類
論文出版年:2020
畢業學年度:108
語文別:英文
論文頁數:85
中文關鍵詞:物理高能物理原子希格斯玻色子Z玻色子光子
外文關鍵詞:high-energy physicsparticle physicsquantum field theorylarge hadron collidercerncompact muon solenoidphotoneuropean organization for nuclear researchz bosonhiggs bosonelementary particlesparticle detectionexperimental particle physicsexperimental high-energy physics
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對 H → Zγ → bbγ 與 Z 玻色子初步調查而以得呈現出有所相
關性。這項分析是以 CMS detector 在√s = 13 TeV 所蒐集的
資料作為基準,並符合 35.9 fb^{−1} 的積分亮度。H 玻色子與 Z
玻色子相關性是由電子與緲子其一的電荷相反輕子重新被組
成。另一方面來說,希格斯玻色子是從Zγ最終產出的bbγ所
重組而成。此分析以兩個 b-tagged 噴流被分成電子與緲子通
道。在信賴水準95%,一個預期排除極限9.681 × 10^4到 4.138
× 10^4乘以電子通道中的標準模型值,而 4.081 × 10^4到 1.836
× 10^4 乘以在緲子通道中的標準模型值,而 3.863 × 10^4 到
1.669 × 10^4在兩者通道組合中。全部介於 120 GeV 到 130 GeV
的質量範圍就可獲得。
A preliminary search for H→Zγ→bbγ produced in association with a Z boson is presented. The analysis is based on the data collected in 2016 with the CMS detector at a center-of-mass energy √s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb^{-1}. The Z boson produced in association with the Higgs boson is reconstructed from a pair of oppositely-charged leptons, either from electrons or muons. On the other hand, the Higgs boson is reconstructed from the Zγ in final states of b¯bγ. The analysis is separated into electron and muon channels with two b-tagged jets. An expected exclusion limit at 95% confidence level of 9.681x10^4 to 4.138x10^4 times the Standard Model value in the electron channel, 4.081x10^4 to 1.836x10^4 times the Standard Model value in the muon channel, and 3.863x10^4 to 1.669x10^4 in the combination of both channels have been obtained in the 120 GeV to 130 GeV mass range.
Contents
1 Introduction and Theory Overview 1
1.1 Introduction ............................... 1
1.2 The Standard Model of elementary particles ............. 1
1.2.1 Quarks and leptons ....................... 3
1.2.2 Quantum electrodynamics .................. 3
1.2.3 Electroweak theory ....................... 4
1.2.4 Spontaneous symmetry breaking ............... 6
1.2.5 Fermion masses ......................... 9
1.2.6 The Higgs boson ........................ 10
1.2.7 Associated vector boson production ............. 11
1.3 H ! Z ................................. 14
1.3.1 Beyond the standard model (BSM) searches ......... 14
1.3.2 Decay rate ............................ 15
2 The LHC and the CMS Detector 17
2.1 The Large Hadron Collider ...................... 17
2.2 The CMS detector ............................ 17
2.2.1 Tracking system ......................... 19
2.2.2 Calorimetry ........................... 19
2.2.3 Muon system .......................... 20
3 Analysis Strategy 23
3.1 Data and simulated samples ...................... 23
3.1.1 Data samples .......................... 23
vii
3.1.2 Simulated samples ....................... 23
Signal samples ......................... 23
Background samples ...................... 25
3.2 Trigger .................................. 25
3.3 Identification of physics objects .................... 26
3.3.1 ZH ! `` + Z ! `+`b¯b ................... 27
Electron ............................. 27
Muon ............................... 28
Photon .............................. 29
b-Jets ............................... 30
b-Tagging ............................ 31
3.4 Event selections ............................. 34
3.4.1 Leptons ............................. 34
3.4.2 Photons ............................. 35
3.4.3 b-Jets ............................... 35
3.4.4 Three-body invariant mass mjj ............... 36
3.4.5 Scaling factors .......................... 37
3.5 Data-MC comparison of kinematic observables ........... 38
3.5.1 Electron channel ........................ 38
3.5.2 Muon channel .......................... 40
4 Signal and Background Estimation 43
4.1 Signal modeling ............................. 43
4.1.1 The three-body invariant mass mjj distribution ...... 43
The double-sided Crystal Ball function ........... 43
4.2 Background modeling ......................... 45
4.2.1 Estimating the turn-on region of the background ...... 45
4.2.2 F-test ............................... 47
4.2.3 Bias study ............................ 48
viii
5 Systematic Uncertainties 53
5.1 Uncertainties on the predicted signal yield ............. 53
5.2 Uncertainties on the shape of the signal model ........... 54
6 Results, Conclusions, and Outlook 57
6.1 Limit setting ............................... 57
6.2 Conclusions and outlook ........................ 60
Bibliography 63
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