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研究生：	波卓洛 Pocholo Luis Pasol Mendiola
論文名稱：	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 Chia-Ming, Kuo
口試委員:
學位類別：	碩士 Master
系所名稱：	理學院 - 物理學系 Department of Physics
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 physics, quantum field theory, cern, european organization for nuclear research, elementary particles, particle detection, experimental particle physics, experimental high-energy physics
相關次數：	點閱：13 下載：0
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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
Introduction and Theory Overview 1
1 Introduction ............................... 1
2 The Standard Model of elementary particles ............. 1
2.1 Quarks and leptons ....................... 3
2.2 Quantum electrodynamics .................. 3
2.3 Electroweak theory ....................... 4
2.4 Spontaneous symmetry breaking ............... 6
2.5 Fermion masses ......................... 9
2.6 The Higgs boson ........................ 10
2.7 Associated vector boson production ............. 11
3 H ! Z ................................. 14
3.1 Beyond the standard model (BSM) searches ......... 14
3.2 Decay rate ............................ 15
The LHC and the CMS Detector 17
1 The Large Hadron Collider ...................... 17
2 The CMS detector ............................ 17
2.1 Tracking system ......................... 19
2.2 Calorimetry ........................... 19
2.3 Muon system .......................... 20
Analysis Strategy 23
1 Data and simulated samples ...................... 23
1.1 Data samples .......................... 23
vii
1.2 Simulated samples ....................... 23
Signal samples ......................... 23
Background samples ...................... 25
2 Trigger .................................. 25
3 Identification of physics objects .................... 26
3.1 ZH ! `` + Z ! `+`b¯b ................... 27
Electron ............................. 27
Muon ............................... 28
Photon .............................. 29
b-Jets ............................... 30
b-Tagging ............................ 31
4 Event selections ............................. 34
4.1 Leptons ............................. 34
4.2 Photons ............................. 35
4.3 b-Jets ............................... 35
4.4 Three-body invariant mass mjj ............... 36
4.5 Scaling factors .......................... 37
5 Data-MC comparison of kinematic observables ........... 38
5.1 Electron channel ........................ 38
5.2 Muon channel .......................... 40
Signal and Background Estimation 43
1 Signal modeling ............................. 43
1.1 The three-body invariant mass mjj distribution ...... 43
The double-sided Crystal Ball function ........... 43
2 Background modeling ......................... 45
2.1 Estimating the turn-on region of the background ...... 45
2.2 F-test ............................... 47
2.3 Bias study ............................ 48
viii
Systematic Uncertainties 53
1 Uncertainties on the predicted signal yield ............. 53
2 Uncertainties on the shape of the signal model ........... 54
Results, Conclusions, and Outlook 57
1 Limit setting ............................... 57
2 Conclusions and outlook ........................ 60
Bibliography 63
                                

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