利用ATLAS偵測器探討由向量玻色子融合產生希格斯玻色子之W玻色子對衰變與其WW背景估計

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研究生：	蔡孟儒 Tsai, Meng-Ju
論文名稱：	利用ATLAS偵測器探討由向量玻色子融合產生希格斯玻色子之W玻色子對衰變與其WW背景估計 Estimation of the WW background in the Vector Boson Fusion H→WW* Analysis with the ATLAS Detector
指導教授：	徐百嫻 Hsu, Pai-hsien
口試委員:	張敬民 Cheung, Kingman 張維甫 Chang, We-Fu
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：	2019
畢業學年度：	107
語文別：	英文
論文頁數：	45
中文關鍵詞：	大強子對撞機、高能實驗、希格斯玻色子、粒子物理
外文關鍵詞：	CERN, Higgs, Experimental High Energy Physics
相關次數：	點閱：1 下載：0
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此論文探討由大強子對撞機以13 TeV能量強度的兩個質子束對撞所產生之數據並藉由ATLAS偵測器所收集，我們研究由向量玻色子融合產生希格斯玻色子之W玻色子對衰變與其WW背景估計。本論文主要提出以mT2來估計WW背景，我們也將詳述實驗結果及未來展望。

We present the analysis strategy for the measurement of the vector boson fusion (VBF) Higgs boson decaying to a pair of W bosons, with 36.1 fb^-1 of proton-proton collisions at center-of-mass energy of 13 TeV collected by the ATLAS detector at the Large Hadron Collider (LHC). We focus on the estimation of irreducible WW background. We utilize a new approach to estimate the WW background using the mT2 variable. The results and future plan of the analysis will be presented.

Contents ................... iii
Lists of Tables ................... iv
Lists of Figures ................... vii
Introduction ................... 1
1: The Discovery of the Higgs Boson ................... 1
2: Overview of the H→WW*→lνlν analysis ................... 3
2.1: Experimental signature ................... 3
2.2: The estimation of WW background ................... 4
The ATLAS experiment ................... 7
1: The ATLAS detector ................... 7
2: Data and MC samples ................... 8
2.1: Data samples ................... 8
2.2: MC samples ................... 9
VBF H→WW*→lνlν analysis ................... 11
1 Common event selection ................... 11
2 Construction of the VBF phase space ................... 12
2.1 Experimental signature of VBF Higgs boson ................... 12
2.2 Observables for background reduction ................... 13
2.3 Topological observables ................... 13
2.4 VBF observables ................... 14
2.5 Event selection for VBF-enriched phase space ................... 15
3 Results of VBF analysis in Run-2 ................... 18
The estimation of WW background ................... 21
1 Normalization factor ................... 21
2 Construction of a WW CR ................... 22
2.1 mT and mT2 variables ................... 22
2.2 Event selection for WW CR/VR ................... 25
3 New WW VR in VBF analysis ................... 26
4 Theory uncertainty of WW background ................... 27
4.1 Reco-truth comparison ................... 28
4.2 Theoretical uncertainties of WW background in the SR ................... 29
Conclusion and Outlook ................... 33
Appendix ................... 34
A Appendix ................... 35
A.1 Event displays for Higgs boson candidates ................... 35
A.2 Re-estimation of WW theoretical uncertainties with the modified pTtot variable ................... 35
A.3 Optimization of the selection for VBF phase space ................... 37
Reference ................... 41


                                

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