發(fā)布時間：2021-08-01 05:28

　　希格斯場是粒子物理標準模型的重要組成部分,它不僅負責(zé)產(chǎn)生基本粒子的質(zhì)量,同時它也是標準模型中唯一的標量粒子。因此對于希格斯玻色子的研究成為了大型強子對撞機（LHC）實驗中的一個熱門課題。大型強子對撞機給我們提供了一個絕好的機會來研究標準模型的預(yù)言以及尋找超越標準模型的新物理現(xiàn)象。在新物理理論中通常會包含一個更加復(fù)雜的希格斯場,因此會產(chǎn)生更多的希格斯波色子,例如一個帶電的希格斯玻色子。尋找這種新粒子將是對新物理模型的一個直接驗證。本博士論文共包含了兩部分主要貢獻:在頂夸克和底夸克衰變道尋找?guī)щ娤８袼共Ｉ樱℉+→tb）;在多輕子末態(tài)尋找標準模型希格斯玻色子伴隨一對頂夸克產(chǎn)生的過程（ttH）。尋找?guī)щ娤８袼共Ｉ拥姆治鍪褂昧薃TLAS探測器在2015和2016年收集到的質(zhì)心系能量13 TeV的質(zhì)子質(zhì)子對撞數(shù)據(jù),對應(yīng)的積分亮度為36.1 fb-1。分析在200 GeV到2000 GeV質(zhì)量區(qū)間沒有發(fā)現(xiàn)相對于標準模型背景的明顯超出,相對于標準模型預(yù)言的最大偏離位于300 GeV質(zhì)量點,對應(yīng)的本地p0值為1.13%。尋找ttH產(chǎn)生的分析使用了 ATLAS探測器在2015年到2017年收集到的數(shù)據(jù)... 

【文章來源】：山東大學(xué)山東省 211工程院校 985工程院校 教育部直屬院校

【文章頁數(shù)】：207 頁

【學(xué)位級別】：博士

【文章目錄】：
摘要
ABSTRACT
Chapter 1 Introduction
Chapter 2 Theory of scalar fields
    2.1 The Standard Model and Higgs Mechanism
        2.1.1 Introduction
        2.1.2 Theory of the Standard Model
            2.1.2.1 Quantum electrodynamics
            2.1.2.2 Quantum chromodynamics
            2.1.2.3 Weak interactions
            2.1.2.4 Higgs mechanism
        2.1.3 SM Higgs boson production and decay at LHC
    2.2 Higgs sector beyond the Standard Model
        2.2.1 Introduction
        2.2.2 Two Higgs doublet model
Chapter 3 LHC & the ATLAS Detector
    3.1 The Large Hadron Collider
    3.2 The ATLAS Detector
        3.2.1 The ATLAS coordinate system
        3.2.2 Inner tracking detector
            3.2.2.1 Pixel detector
            3.2.2.2 Semiconductor tracker (SCT)
            3.2.2.3 Transition Radiation Tracker(TRT)
        3.2.3 Calorimeter
            3.2.3.1 Electromagnetic calorimeter
            3.2.3.2 Hadronic calorimeter
        3.2.4 Muon spectrometer
            3.2.4.1 Muon precision detectors
            3.2.4.2 Muon trigger detectors
        3.2.5 Trigger
        3.2.6 Magnetic systems
        3.2.7 Simulation of ATLAS detectors
    3.3 Upgrade of Inner Detector towards High-Luminosity LHC(HL-LHC): the Inner Tracker project (ITk)
    3.4 Object reconstruction
        3.4.1 Electrons
            3.4.1.1 Reconstruction
            3.4.1.2 identification
        3.4.2 Photons (γ)
        3.4.3 Muons
            3.4.3.1 Reconstruction
            3.4.3.2 Identification
        3.4.4 The (τ) lepton
        3.4.5 Jets
            3.4.5.1 Reconstruction
            3.4.5.2 Calibration and Systematics
            3.4.5.3 b-jets tagging
        3.4.6 Missing transverse energy
Chapter 4 Search for a heavy charged Higgs boson decaying totop and bottom quarks
    4.1 Introduction
    4.2 Overview of previous results
    4.3 Analysis strategy
        4.3.1 Data, Signal and background modelling
            4.3.1.1 Data samples
            4.3.1.2 Signal samples
            4.3.1.3 Background samples
        4.3.2 Selections
        4.3.3 Background estimation
        4.3.4 Multivariate analysis
            4.3.4.1 Brief concepts of BDT
            4.3.4.2 Classification BDT in di-lepton final states
    4.4 Mass reconstrution in di-lepton final states
        4.4.1 Introduction
        4.4.2 Reconstruction BDT Training
        4.4.3 Application to the analysis
    4.5 Results
        4.5.1 Systematic uncertainties
            4.5.1.1 Instrumental uncertainties
            4.5.1.2 Theoretical uncertainties
        4.5.2 Statistical study
            4.5.2.1 Statistical model
            4.5.2.2 Fit results
            4.5.2.3 interpretation
            4.5.2.4 CMS results
Chapter 5 Search for the production of Higgs boson associatedwith a pair of top quarks in multilepton final states
    5.1 Introduction
    5.2 Personal contributions
    5.3 Analysis strategy of ttH multilepton with 80 fb-1 Data
        5.3.1 Data and Monte Carlo samples
        5.3.2 Signal region definition and signal extraction
        5.3.3 MVA analysis
            5.3.3.1 2lSS 2D analysis strategy
            5.3.3.2 3l multiclass BDT
        5.3.4 Background estimate
            5.3.4.1 Template fit
    5.4 Study of 2lSS+1τ_(had) final state
        5.4.1 Event selection
        5.4.2 Categories analysis optimization
            5.4.2.1 Validation of categorization optimization
        5.4.3 Non-prompt backgrounds
            5.4.3.1 Electron charge flip (QMisID)
            5.4.3.2 Fake tau
            5.4.3.3 Fake light leptons
                5.4.3.3.1 Fake factor
                5.4.3.3.2 Matrix method
                5.4.3.3.3 Template fit
        5.4.4 Statistical interpretation
            5.4.4.1 Choice of analysis configurations
            5.4.4.2 Previous results
            5.4.4.3 Current results
            5.4.4.4 Alternative approach
            5.4.4.5 Summary
    5.5 Results of ttH multilepton analysis
        5.5.1 Comparison with CMS results
Chapter 6 Conclusion
Bibliography
致謝
附件



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