利用CMS探測器測量Wγ的偶合｜國立中央大學博碩士論文系統

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研究生：	李學威 Syue-Wei Li
論文名稱：	利用CMS探測器測量Wγ的偶合 The measurement of Wγ production in CMS
指導教授：	林宗泰 Willis T. Lin
口試委員:
學位類別：	博士 Doctor
系所名稱：	理學院 - 物理學系 Department of Physics
畢業學年度：	98
語文別：	英文
論文頁數：	57
中文關鍵詞：	高能實驗
外文關鍵詞：	aTGC, CMS, di-boson
相關次數：	點閱：9 下載：0
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查詢本校圖書館目錄查詢臺灣博碩士論文知識加值系統勘誤回報

電弱理論包含了玻色子偶合並且適當地描述光子與W玻色子間的偶合。新物理可能影響玻色子自身的交互作用和改變動量的分布（例如：增加cross section，與標準模型比較，光子的橫向動量（pT）增加）。因此，對於Ｗγ的測量可以提供一個好的機會去測試電弱理論的結構。這篇論文利用CMS探測器分析Ｗγ的cross section並選擇W衰變為電子當作訊號事件。這篇論文也利用數據分析去估算背景事件。最後，Ｗγ的測量cross section為12.5±2.0（系統誤差）pb。

The electroweak (EW) theory includes the tri-linear vector boson coupling and well describes the coupling of the photon to the W boson. New physics may affect the self-interactions of vector bosons and alter the kinematic distributions, for example, enhanced cross section and higher photon pT excess as compared to the Standard Model. Thus, the measurements of Wγ production provide a good opportunity to test the structure of the non-Abelian character of EW theory. This thesis presents a study for the cross-section measurement of Wγ production with electron and photon in final state at CMS at sqrt(s) = 10 TeV. A data-driven method of estimating background is also shown and the measured cross-section of Wγ production is 12.5 ± 2.0 (syst.) pb.

Chapter 1 Introduction ··· 1
1 The Standard Model ··· 1
2 The Electroweak Theory ··· 2
3 Theory of Wγ Production ··· 3
Chapter 2 The CMS Experiment at LHC ··· 7
1 Large Hadron Collider ··· 7
2 Physics Motivations ··· 8
3 Detector Requirements ··· 9
4 Compact Muon Solenoid ··· 10
4.1 Coordinate Conventions ··· 10
4.2 Magnet ··· 11
4.3 Muon System ··· 12
4.4 Hadron Calorimeter ··· 12
4.5 Electromagnetic Calorimeter ··· 14
4.6 Tracker System ··· 14
4.6.1 Strip Tracker ··· 16
4.6.2 Pixel Tracker ··· 16
5 Trigger and Data Acquisition ··· 17
5.1 Level-1 Trigger ··· 17
5.2 High-Level Trigger ··· 17
Chapter 3 The Performance of ECAL Preshower in 2007 Test Beam··· 19
1 Introduction ··· 19
2 Test Beam Setup and the Preshower Signal Reconstruction ··· 19
3 Preshower MIP Calibration ··· 22
3.1 MIP Calibration in HG ··· 22
3.2 MIP Calibration in LG ··· 24
4 MIP Cross Check and Additional Correction ··· 24
5 Preliminary Result of Combined EE and ES Energy ··· 26
Chapter 4 The Reconstructions ··· 28
1 Electrons and Photons ··· 28
1.1 Superclustering Algorithms ··· 28
1.1.1 Hybrid Barrel Supercluster ··· 28
1.1.2 Multi5×5 Endcap Supercluster ··· 28
1.2 Position measurement ··· 29
1.3 Photon Reconstruction ··· 30
1.4 Electron Reconstruction ··· 31
1.4.1 Electron Clustering ··· 31
1.4.2 Electron Energy Scale Corrections ··· 31
1.4.3 Electron Tracking ··· 32
1.4.4 Combination of Energy and Momentumum Measurements ··· 32
2 Missing Transverse Energy ··· 33
Chapter 5 Wγ Production Cross Section ··· 35
1 Introduction ··· 35
2 Data Samples ··· 35
3 Event Selections ··· 37
3.1 Trigger Requirement ··· 38
3.2 Photon ··· 38
3.3 Electron ··· 39
3.4 W Selection ··· 41
3.5 Electron-photon Separation ··· 42
3.6 Electron-photon Mass Cut ··· 43
4 Photon pT Distribution and Event Yields ··· 43
5 Background Estimation ··· 44
5.1 Determination of Ratio ··· 45
5.1.1 Validate the Ratio Distributions ··· 45
5.1.2 Extracted the parameters ··· 46
5.2 W+jet Estimation ··· 46
6 Acceptance ··· 46
7 Efficiencies ··· 48
7.1 Efficiency for Electron Reconstruction ··· 49
7.2 Efficiency for Electron Identification ··· 50
8 Systematic Uncertainties ··· 50
Chapter 6 Conclusion ··· 54
Appendix A: Expected Yields with Step-by-step Selection ··· 55
Appendix B: Ratio Method ··· 56

                                

Chapter1:
[1] U. Baur et al., “QCD corrections to hadronic Wγ production with nonstandard WWγ couplings” Phys. Rev. D48 5140 (1993).
[2] K. Hagiwara et al., Ncul. Phys. B282, 253 (1987); U. Baur and D. Zeppendfeld, ibid. B308, 127 (1988); K. Gaemers and G. Gounaris, Z. Phys. C 1, 59 (1979).
[3] W. J. Marciano et al., “Bound on the W-boson electric dipole momentum,” Phys. Rev. D 33, 3449.
[4].F. Boudjema et al., “Anomalous momentums of quarks and leptons from nonstandard WWγ couplings,” Phys. Rev. D 43, 2223.
Chapter2:
[1] CMS Physics TDR Vol. 1, CERN/LHCC/2006-001.
Chapter3:
[1] CMS Physics TDR Vol. 1, CERN/LHCC/2006-001. [2] I. Evangelou, Nuclear Instruments and Methods in Physics Research Section A, Volume 572, Issue 2, p.
624-632. [3] P. Aspell et al., CMS-NOTE 2000–001.
Chapter4:
[1] E. Meschi et al, Electron reconstruction in the cms electromagnetic calorimeter. CMS NOTE-2001/034.
[2] N. Adam et al, Electron reconstruction at low pT. CMS AN-2009/074.
[3] S. Baffioni et al, Electron reconstruction in CMS. CMS NOTE-2006/40.
[4] C. Charlot et al, Reconstruction of electron tracks using Gaussian Sum Filter in CMS. CMS AN-2005/011.
[5] S. Esen et al, MET performance in CMS. CMS AN-2007/041.
Chapter6:
[1].T. Sjostrand et al., “High-energy-physics event generation with PYTHIA 6.1,” Comput. Phys. Commun. 135 (2001) 238.259, arXiv:hep-ph/0010017.
[2].M.L. Mangano et al., “ALPGEN, a generator for hard multiparton processes in hadronic collisions.” arXiv:hep-ph/0206293.
[3] G. Alexander and I. Cohen, “The source size dependence on the M(hadron) applying Fermi and Bose statistic and I-spin invariance,” arXiv:hep-ph/9909288.
[4] https://twiki.cern.ch/twiki/bin/view/CMS/HLTMenuTriggerDescriptions.
[5] https://twiki.cern.ch/twiki/bin/view/CMS/PhotonIDAnalysis.
[6] N. Adam et al., “Towards a Measurements of the Inclusive Weν and Zee Cross Section in pp Collisions at = 10 TeV,” CMS AN-2009/98.
[7].https://twiki.cern.ch/twiki/bin/view/CMS/SWGuideEgammaIsolationIn2_1And2_2AndPlansFor3_0
[8] G.J. Pawloski, “The study of Wγ production at D0,” PhD Thesis in 2007.
[9] G. Daskalakis et al., “Measuring Electron Efficiencies at CMS with Early Data,” CMS AN-2007/019.
[10] CMS Collaboration, “Plan for Jet Energy Corrections at CMS,” CMS PAS JME-07-002.
[11] J. D’Hondt et al., “Measurement of jet energy scale corrections using top quark events,” CMS AN-2007/029
[12] D. Bourilkov, R. C. Group, and M. R. Whalley, “LHAPDF: PDF use from the Tevatron to the LHC,” arXiv:hep-ph/0605240v2.
[13] P. M. Nadolsky and Z. Sullivan, .PDF uncertainties in WH production at Tevatron,. arXiv:hep-ph/0110378v2.

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