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| ???org.dspace.app.webui.jsptag.ItemTag.dcfield??? | Value | Language |
|---|---|---|
| dc.contributor.advisor | 陳凱風(Kai-Feng Chen) | |
| dc.contributor.author | Chun-Ting Lin | en |
| dc.contributor.author | 林俊廷 | zh_TW |
| dc.date.accessioned | 2021-06-16T22:56:49Z | - |
| dc.date.available | 2020-03-03 | |
| dc.date.copyright | 2020-03-03 | |
| dc.date.issued | 2020 | |
| dc.date.submitted | 2020-02-26 | |
| dc.identifier.citation | [1] “The LHC Schematic”. https://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/lhc_in_pictures.htm. Accessed: 2020-01-04.
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| dc.identifier.uri | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/64639 | - |
| dc.description.abstract | 本研究旨在尋找頂夸克經由變味中性流衰變之事件，而此衰變事件在標準
模型中是被GIM 機制所高度抑制的。其中，頂夸克經此機制衰變至一個上夸克 (或魅夸克)與一個Z 玻色子的衰變比率被理論預測約為10−14數量級。然而，根 據許多標準模型的延伸理論預測，此衰變比率是可以提升至10−4數量級的。 本研究中將會著重分析頂夸克與反頂夸克對事件，其中一個頂夸克會衰變 至一個底夸克與一個W 玻色子，而另一頂夸克將會衰變至一個上夸克(或魅夸 克)與一個Z 玻色子，而W 和Z 玻色子都將會衰變成輕子對。本研究所分析的數 據為緊湊緲子線圈偵測器在2016 與2017 年所蒐集的質心能量為13 兆電子伏特 之質子質子對撞數據，其合計總通量為77.4fb−1。經由本研究所得知，無顯著 超量的期望訊號事件數，而經由計算可得頂夸克衰變至一個上夸克(或魅夸克) 與一個Z 玻色子的預期衰變比率在2016 年之數據中不超過0.027%(0.032%)， 而在2017 之數據中不超過0.021%(0.025%)。 關鍵字詞: “變味中性流”， “頂夸克”， “緊湊緲子線圈偵測器” | zh_TW |
| dc.description.abstract | This analysis searches for the top quark decay through the flavor changing neutral
current (FCNC) process which is highly suppressed by the Glashow-Iliopoulos- Maiani (GIM) mechanism in Standard Model (SM) and the branching fraction for a top quark decaying into a charm or up quark and a Z boson is predicted to be of the order 10−14. However, several extensions of the SM theories predict the branching fraction of FCNC can be enhanced up to the order of 10−4 . The data collisions is collected with the CMS detector in 2016 and 2017 from pp collision at the centre-of-mass energy of 13 TeV and an integrated luminosity of 77.4 fb−1. This analysis focuses on the top quark-antiquark events in which one of the top quark decays to a bottom quark and a W boson and the other top quark decays to a light quark(u, c) and a Z boson. Both the W and Z boson will decay into lepton pairs. No significant excess is observed in the data. The expected upper limits are set on the branching fraction of the top decays: Br(t −! uZ) < 0.027% and Br(t −! cZ) < 0.032% for 2016 and Br(t −! uZ) < 0.021% and Br(t −! cZ) < 0.026% for 2017 at the 95% confidence level. Keyword : ”FCNC”, ”top quark”, ”CMS” | en |
| dc.description.provenance | Made available in DSpace on 2021-06-16T22:56:49Z (GMT). No. of bitstreams: 1 ntu-109-R05244005-1.pdf: 6587791 bytes, checksum: 558b4375ac7d0c0af1f0ccad3c0535ce (MD5) Previous issue date: 2020 | en |
| dc.description.tableofcontents | 1 Introduction 1
1.1 The top quark in Standard Model . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Flavor Changing Neutral Current in top quark decay . . . . . . . . . . . . . 2 1.3 Overview of the analysis strategy . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Experimental Apparatus 5 2.1 Large Hadron Collider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Compact Muon Solenoid Detector . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2.1 Magnetic Configuration . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2.2 Inner Tracking System . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2.3 Electromagnetic Calorimeter (ECAL) . . . . . . . . . . . . . . . . . . 8 2.2.4 Hadronic Calorimeter(HCAL) . . . . . . . . . . . . . . . . . . . . . . 8 2.2.5 Muon Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2.6 Trigger System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3 Data and Monte Carlo Samples 12 3.1 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.2 MC Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4 Physical Object Reconstruction 16 4.1 Track Reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.2 Vertex Reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4.3 Muon Reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.4 Electron Reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.5 Missing transverse energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.6 Jet Reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.7 b-jet Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5 Event Selection 22 5.1 High Level Trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5.2 Muon Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5.3 Electron Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 5.4 Jet Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 5.5 Event Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 6 Correction to simulations 29 6.1 Pileup re-weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 6.2 Leptons efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 6.3 Jet energy resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 6.4 DeepCSV shape correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 6.5 Kinematic distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 7 Background Estimation 35 7.1 Event Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 7.1.1 Maximum-Likelihood Method . . . . . . . . . . . . . . . . . . . . . . 36 7.1.2 Extended Likelihood Function . . . . . . . . . . . . . . . . . . . . . . 37 7.2 WZ control region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 7.3 TT control region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 8 Analysis Strategy 44 8.1 One Candidate per event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 8.2 MVA for Best Candidate Choice . . . . . . . . . . . . . . . . . . . . . . . . . 45 8.3 MVA for Signal Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 9 Systematic Uncertainties 51 9.1 Luminosity Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 9.2 Pileup re-weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 9.3 Trigger Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 9.4 Lepton Efficiency Scale Factors . . . . . . . . . . . . . . . . . . . . . . . . . 52 9.5 b tagging Scale Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 9.6 Jet Energy Correction and Resolution . . . . . . . . . . . . . . . . . . . . . 52 9.7 Parton Distribution Function . . . . . . . . . . . . . . . . . . . . . . . . . . 52 9.8 Background Normalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 10 Limit Calculation and Conclusion 56 10.1 Limit calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 10.2 Conclusion and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 A Estimation of the trigger efficiency 58 B Transfer Ratio of Background Estimation 59 B.1 Transfer Factor in WZCR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 B.2 Transfer Factor in TTCR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 C The MVA configuration 61 C.1 2016 tuZ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 C.1.1 Best Combination Choice . . . . . . . . . . . . . . . . . . . . . . . . 61 C.1.2 Signal Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 C.2 2017 tcZ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 C.2.1 Best Combination Choice . . . . . . . . . . . . . . . . . . . . . . . . 66 C.2.2 Signal Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 C.3 2017 tuZ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 C.3.1 Best Combination Choice . . . . . . . . . . . . . . . . . . . . . . . . 70 C.3.2 Signal Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 References 74 | |
| dc.language.iso | en | |
| dc.title | 於 CMS 實驗質心能量 13TeV 質子對撞資料中尋找頂夸克衰變到 Z 玻色子與輕夸克之變味中性流事件 | zh_TW |
| dc.title | Search for Flavor Changing Neutral Currents Decays in t→qZ at centre-of-mass energy of 13 TeV in CMS | en |
| dc.type | Thesis | |
| dc.date.schoolyear | 108-1 | |
| dc.description.degree | 碩士 | |
| dc.contributor.oralexamcommittee | 張寶棣(Pao-Ti Chang),王名儒(Ming-Zu Wang),余欣珊(Shin-Shan Yu) | |
| dc.subject.keyword | 變味中性流,頂夸克,緊湊緲子線圈偵測器, | zh_TW |
| dc.subject.keyword | FCNC,top quark,CMS, | en |
| dc.relation.page | 75 | |
| dc.identifier.doi | 10.6342/NTU202000610 | |
| dc.rights.note | 有償授權 | |
| dc.date.accepted | 2020-02-26 | |
| dc.contributor.author-college | 理學院 | zh_TW |
| dc.contributor.author-dept | 天文物理研究所 | zh_TW |
| Appears in Collections: | 天文物理研究所 | |
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| ntu-109-1.pdf Restricted Access | 6.43 MB | Adobe PDF |
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