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研究生： 吳季函
Wu, Ji-Han
論文名稱： 重微中子衰變為兩個輕子與一個微中子的模擬數據之分析
The Analysis of Heavy Neutrino Simulation Data in N→lW→2lv Channel
指導教授： 張敬民
Cheung, Kingman
口試委員: 曾柏彥
Tseng, Po-Yen
阮自強
Yuan, Tzu-Chiang
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： 2021
畢業學年度： 109
語文別： 英文
論文頁數： 23
中文關鍵詞： 高能物理 、粒子物理 、重微中子
外文關鍵詞： high energy physics, particle physics, heavy neutrino
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    • 本研究介紹可以解釋微中子質量來源的重微中子模型，並聚焦在電子重微中子 衰變反應N → e + W 且最終產物為三個可被探測之輕子的反應。研究部分主要將該反應輸入蒙地卡羅模擬器並比較了重微中子訊號與標準模型背景訊號 的統計上限。而相關參數設定成加速粒子數密度為35.0(fb inverse)，質心座標 系能量為13 TeV，重微中子混合角為0.1。結果顯示當重微中子質量設定在100 GeV到1000 GeV時，三輕子最終態的訊號比雙同號輕子與雙噴流最終態的訊號更顯著。

    The study introduces the heavy neutrino model, which explains that a neutrino’s mass comes from the seesaw mechanism. We focus on the decay of electron heavy neutrino N → e + W , and the signal is the final state of three detectable leptons with an electron neutrino as missing energy. This study focuses on comparing the Standard Model backgrounds and computations of the upper limit of heavy neutrino. Given the luminosity 35.0 fb−1, center-of-mass energy 13 TeV and mixing angle 0.1, the results show that the signal of the three leptons final state is more significant than the signal of two same-sign leptons and two jets when the mass was set in 100 GeV to 1000 GeV.

    Contents ii List of Tables iii List of Figures iv 1 Introduction 1 2 Formalism for Dirac Heavy neutrino 2 2.1 Seesawmechanism .............................. 2 2.2 AmplitudeofHeavyneutrino ........................ 4 3 Monte Carlo samples generation 6 3.1 Heavyneutrinoprocesswithfinalstate................... 6 4 Detector Simulation and Events Selection 9 4.1 DetectorSimulation ............................. 9 4.2 EventsPreselection.............................. 10 i 4.3 KinematicVariablesCut........................... 10 4.4 EfficiencyTable................................ 11 5 Background Estimation 15 5.1 WZBackground ............................... 15 5.2 ZZBackground................................ 16 6 Result 17 6.1 Analysis.................................... 17 6.2 Upperlimitdiagrams............................. 18 7 Conclusion 20 Appendix 20 A Appendix 21 A.1 MadGraphCode ............................... 21

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    [3] CMS Collaboration. “Search for heavy Majorana neutrinos in same-sign dilep- ton channels in proton-proton collisions at √s = 13 TeVn”. In: 2019.9 (Sept. 2019). issn: 1126-6708. doi: 10.1007/JHEP01(2019)122. url: http://dx. doi.org/10.1007/JHEP01(2019)122.

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