Search for leptonic WZγ production in LHC pp collisions at √s = 13 TeV and constraints on anomalous quartic gauge couplings
질량중심에너지 13 TeV의 양성자-양성자 충돌실험에서 렙톤으로 붕괴하는 모드를 통하여 WZγ 보손이 생성되는 프로세스 탐색과 비정상적인 사중 게이지 결합에 대한 제약
- 발행기관 경북대학교 대학원
- 지도교수 도움말 Chang-Seong Moon
- 발행년도 2023
- 학위수여년월 2024. 2
- 학위명 박사
- 학과 및 전공 도움말 일반대학원 물리학과
- 세부분야 해당없음
- 원문페이지 xiv, 147 p.
- 실제URI http://www.dcollection.net/handler/knu/000000106563
- UCI I804:22001-000000106563
- 본문언어 영어
- 참고문헌 p.105-109
- 저작권 경북대학교 논문은 저작권에 의해 보호받습니다.
초록/요약 도움말
표준 모형 중 드물게 발생하는 프로세스인 W Zγ 보손이 양성자-양성자 충돌로 부 터 생성되어 렙톤으로 붕괴하는 모드를 탐색하였다. 질량 중심 에너지가 13 TeV 에서 CMS 검출기로 2016-2018년 동안 획득한 총 138 fb−1 의 시뮬레이션 데이 터를 분석하여 3.6 σ의 expected significance를 얻었다. 또한 2018년동안 획득한 59.7 fb−1의 검출기 데이터를 분석하여 3.6 σ의 observed significance를 얻었다. WZγ 프로세스로 표준 모형 뿐만 아니라, 같은 데이터 분석 기법을 사용하여 새로 운 물리 존재 여부도 탐색하였다. 유효장 이론 중 하나인 비정상 4차 게이지 보손 커플링 모델을 통하여 8차원 연산자의 결합 상수에 대한 95% confidence inter- val을 구하였다. 또한, 공동 연구 팀인 북경대학교 팀에서 진행중인 Photophobic Axion-like-particle 모델 연구를 부록에서 소개한다. 새로운 물리에 대한 연구는 표준모형 예측을 벗어나지 않았으므로, 새로운 물리에 대한 실험적 증거는 발견 되지 않았다.
more초록/요약 도움말
The research on the production of different gauge bosons, specifically WZγ , is presented. The W and Z bosons decay leptonically, resulting in final states that include triple leptons, photons, and neutrino. The analyzed data corresponds to an integrated luminosity of 138 fb−1 from proton-proton collisions at s = 13 TeV, collected by the CMS detector at the Large Hadron Collider between 2016 and 2018. The signal and background samples are generated using Monte Carlo simulations produced by the official CMS Generator group. Non-prompt photon and lepton backgrounds are modeled using a data-driven method and validated in each control region. The ex- pected significance is calculated through a one-dimensional fit using the HiggsCom- bined tool framework. Three control regions (ZZ, Non-prompt lepton, and photon) and one signal region are defined and fitted simultaneously. Mlll is utilized for ZZ and fake lepton control region, while Mllγ is used for the signal region and fake photon region. The obtained expected significance is 3.6 σ . The limited unblinding analysis is performed using 2018 dataset. The observed significance of 2018 dataset is measured 3.6 σ with signal strength of 1.6+0.6−0.5 (Sys+Stat). The exclusion limits of anomalous quartic gauge couplings in terms of dimension- 8 effective field theory Willson’s coefficient (FM0−5,7/Λ4 and FT0,1,2,5−9/Λ4) are calculated using WZγ process. While employing the same signal region as in the Standard Model WZγ analysis, the photon pT cut of 60 GeV is added and the last bin of the Mlllγ distribution (Mlllγ > 600 GeV) is used in the limit calculation. This additional consideration is necessary because photons associated with anoma- lous quartic gauge couplings exhibit enhanced momentum. The expected limits for Run-II dataset and observed limit for 2018 dataset are measured. The results are comparable with other triple-boson production analysis. Additionally, the search for Axion-like particles, with their decay into Zγ , is added in the Appendix. This analysis is performed by our collaborator, the Peking University group The 95% two-dimensional limits on coupling parameter 1/ fa and Axion-like-particle mass are investigated. No excess of events above the standard model background is ob- served for both new physics searches.
more목차 도움말
1 Introduction 1
2 Theoretical Motivation 4
2.1 The Standard Model 4
2.1.1 Particles 5
2.1.2 Fundamental interactions 7
2.1.3 Multiboson production 8
2.1.4 WZγ production 8
2.2 Anomalous Quartic Gauge Boson Coupling 9
2.3 Axion-Like Particle Search 11
3 Experimental Apparatus 14
3.1 Accelerator: Large Hadron Collider 14
3.1.1 Accelerator Complex 15
3.1.2 Experiments 16
3.1.3 Accelerator running plan 16
3.2 Detector: Compact Muon Solenoid 17
3.2.1 Superconducting Solenoid 18
3.2.2 Tracking detector 18
3.2.3 Electromagnetic Calorimeter 19
3.2.4 Hadron Calorimeter 19
3.2.5 Muon chamber and Return Yoke 19
3.2.6 Main detector components for this analysis 20
3.3 Trigger and Data Acquisition System 22
3.3.1 Level 1 trigger 22
3.3.2 Level 2 trigger 25
4 Data and Monte Carlo samples 27
4.1 Data 27
4.2 Trigger 29
4.3 Monte Carlo samples 30
5 Background Estimation 40
5.1 ZZ background 40
5.2 Fake lepton estimation 41
5.3 Fake photon estimation 51
6 Object and Event Selection 64
6.1 Muons 65
6.2 Electrons 66
6.3 Photons 68
6.4 Jets and MET 70
6.5 Event Selection 70
7 Systematic Uncertainties 77
7.1 Detector 77
7.2 Algorithms 78
7.3 Data driven method 80
7.3.1 Fake Lepton 81
7.3.2 Fake Photon 81
7.4 Uncertainties with theoretical models 82
8 Results and Interpretations 84
8.1 SM WZγ Signal Extraction 84
8.2 Interpretation to aQGC 90
8.2.1 Sample generation 90
8.2.2 aQGC WZγ signal region 90
8.2.3 Limit calculation 94
8.2.4 Unblinded analysis 97
9 Conclusion 103
A aQGC plots for full Run-II data
B Interpretation to Photophobic Axion-Like Particle search
B.0.1 Sample generation
B.0.2 Limit calculation
C Current researches of the multi-boson production
D Non-prompt lepton closure test
E Other works : Large-scale deep learning for multi-jet event classification
E.1 Introduction
E.2 Model
E.3 Results
E.4 Conclusion
E.5 References
