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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