跳到主要內容

臺灣博碩士論文加值系統

(44.201.97.0) 您好!臺灣時間:2024/04/24 11:20
字體大小: 字級放大   字級縮小   預設字形  
回查詢結果 :::

詳目顯示

我願授權國圖
: 
twitterline
研究生:陳以牧
研究生(外文):Yi-Mu Chen
論文名稱:於緊湊緲子線圈質心能量十三兆電子伏特尋找激發態頂夸克成對生成事件
論文名稱(外文):Search for excited top quark pair production in lepton plus jets final state with √s = 13 TeV at CMS
指導教授:陳凱風
口試委員:裴斯達余欣珊張寶棣
口試委員(外文):Stathes Paganis
口試日期:2017-06-26
學位類別:碩士
校院名稱:國立臺灣大學
系所名稱:物理學研究所
學門:自然科學學門
學類:物理學類
論文種類:學術論文
論文出版年:2017
畢業學年度:105
語文別:英文
論文頁數:145
中文關鍵詞:激發態頂夸克自旋 3/2 夸克輕子加噴流超弦共振
外文關鍵詞:excited top quarkspin-3/2 quarklepton plus jetstring resonance
相關次數:
  • 被引用被引用:0
  • 點閱點閱:252
  • 評分評分:
  • 下載下載:0
  • 收藏至我的研究室書目清單書目收藏:0
本研究利用大強子對撞機上的緊湊緲子線圈偵測器所收集到質心能量 13 兆電子伏特的質子對撞事件中,尋找自旋 3/2 激發態頂夸克成對生成事件。在藍氏–桑氏模型中,激發態頂夸克將衰變成頂夸克和膠子。
本分析關注之事件為頂夸克對衰變成兩個底夸克與兩個 W 玻色子,其中一個 W 玻色子繼續衰變成的兩個夸克,另一個 W 玻色子衰變成帶電輕子 (電子或緲子) 及微中子。被納入分析之對撞事件,其最終態必須有一個孤立輕子、橫量動量不對稱、以及至少六個噴流;其中兩個噴流的性質必須與底夸克經強作用分裂所形成的噴流性質相容。
本分析嘗試將事件中的運動變量重建為激發態頂夸克物件,以重建質量作為信號、背景事件的判別變量,並藉最大似然回歸分析分離觀察資料之質譜中信號與背景事件數量。
緊湊緲子線圈偵測器在 2016 年蒐集之累積光度 35.9 逆飛靶恩的實驗數據,與標準模型預測並無顯著性差異。推斷在 95% 的信心水準下質量小於 1.2 兆電子伏特等效質量的自旋 3/2 激發態頂夸克不存在。
This research searches for the pair production of spin-3/2 excited top quarks (t* t-*) in an extension of the Randall-Sundrum model with each excited t* decaying to a top quark and a gluon, using the data collected in 2016 with the CMS detector from pp collisions with a centre-of-mass energy of 13 TeV, and an integrated luminosity of 35.9 fb−1 .
The search focuses on the semileptonic decay of the top quark pairs, with one top quarks decaying to a b quark plus two additional quarks from a hadronically decaying W boson, and the other top quark decaying to a b quark plus a lepton (muon or electron) and a neutrino from a leptonically decaying W boson. The observed final state of events that are selected for analysis requires an isolated muon or electron, an imbalance in transverse momentum, and at least six jets, two of which must be compatible with originating from the fragmentation of a b quark.
The strategy of the analysis focuses on a kinematic reconstruction of t* objects,
using the reconstruction mass as the discriminating variable for distinguishing between signal and background events. Extraction of potential signal events in data is obtained from an unbinned maximum likelihood fit of a signal-plus-background model to the observed mass spectrum. The data shows no significant excess over standard model predictions, and a lower limit of 1.2 TeV/c2 at 95% confidence level on the mass of the spin-3/2 t* quark model is set.
1 Introduction
1.1 The standard model top quark - 1
1.2 Excited top quark models - 3
1.3 Overview of analysis strategy - 4
2 Experimental Apparatus
2.1 The large hadron collider - 7
2.2 The compact muon solenoid detector - 8
2.2.1 Coordinate system - 10
2.2.2 Magnet configuration - 10
2.2.3 Tracking subsystem - 11
2.2.4 Electromagnetic calorimeter (ECAL) - 13
2.2.5 Hadronic calorimeter (HCAL) - 15
2.2.6 Muon detectors - 16
2.2.7 Trigger system - 18
2.3 Luminosity measurement -19
3 Physical object reconstruction at CMS
3.1 Particle flow ingredients - 21
3.1.1 Track - 21
3.1.2 Vertex - 23
3.1.3 Calorimeter clustering - 25
3.2 Ingredient linking and particle-flow identification - 25
3.3 Jets - 27
3.3.1 Jet clustering algorithm- 27
3.3.2 Jet corrections and resolution - 27
3.4 Object quality and properties - 28
3.4.1 Muon identification and isolation algorithms -29
3.4.2 Electron identification and isolation algorithms - 30
3.4.3 Lepton efficiencies - 32
3.4.4 Jet identification -34
3.4.5 Jet flavour tagging - 34
4 Data and simulated samples
4.1 Data samples- 39
4.2 Simulated samples - 40
4.2.1 Stages of simulation - 40
4.2.2 Parton distribution functions - 41
4.2.3 Simulation used in analysis - 42
4.3 Corrections to simulation - 43
4.3.1 Jet energy smearing- 43
4.3.2 Efficiency scale factor- 45
4.3.3 Pileup re-weighting - 45
5 Event selection
5.1 Trigger - 49
5.2 Physical object selection -49
5.3 Event Selection - 50
5.4 Selection Results - 51
6Reconstructing the excited top system
6.1 General strategy for mass reconstruction- 57
6.2 Simple sorting algorithm- 58
6.3 Kinematic constrained reconstruction - 62
6.4 Results with simulated signal, background and data -63
7Signal and background estimation
7.1 Signal shape modelling – adaptive kernel estimation - 67
7.2 Determining a parametric description of background - 68
7.2.1 Unbinned maximum likelihood fit - 70
7.2.2 Goodness of fit — Kolmogorov–Smirnov test - 71
7.2.3 Number of parameters in parametric fit — likelihood ratio test - 71
7.2.4 Stability and bias test of fit - 72
7.3 Signal and background extraction from data - 73
8 Systematic uncertainties
8.1 Simulation correction - 79
8.2 Jet energy correction and resolution - 80
8.3 PDF and QCD scale uncertainties - 80
8.3.1 Treatment of uncertainties - 83
8.3.2 Meaning of the uncertainty weights - 84
8.4 Signal modelling - 84
8.5 Other uncertainties - 85
Summary of uncertainties - 85
9 Limit calculation
9.1 Asymptotic CLs limit - 87
9.1.1 Test statistic of the CLs method - 87
9.1.2 Limit of an experiment - 88
9.1.3 Asymptotic formula for test statistic distributions - 90
9.2 Treatment of uncertainties obtained in analysis -91
9.3 Results of limit calculation - 92
10 Summary and outlook
10.1 Brief summary of analysis - 95
10.2 Outlook on future improvement - 95

A Electron trigger study - 101
A.1 Object, event and sample selection - 101
A.2 Results of tag and probe - 102
A.3 Determining the systematic uncertainty - 103
B Uniform approach to the interpretation of uncertainty and error propagation
B.1 Defining error -105
B.1.1 Frequentist definition of confidence interval-105
B.1.2 Bayesian definition of error - 108
B.1.3 A compromise method - definition of Minos error interval - 109
B.2 Error propagation through a function - 110
B.3 Fast estimate of multiple variable error propagation - 111
B.4 Evaluation of multiple variable error propagation - 113
B.5 Estimating the likelihood function from an given error - 115
B.6 Summary of approach - 118
C Additional plots used in analysis
C.1 All signal+background fit results using data - 119
C.2 Plots used for background stability analysis - 123
C.2.1 Additional pull distribution summary diagrams - 123
C.2.2 All pull distribution for pseudo experiments conducted - 125
C.2.3 Pull distribution of pseudo experiments with shifted background and signal samples- 133
D References 141
1 CMS, “Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC”, Phys. Lett. B716, 30–61 (2012).
2 ATLAS, “Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC”, Phys. Lett. B716, 1–29 (2012).
3 ATLAS and C. Collaborations, “Combined Measurement of the Higgs Boson Mass in pp Collisions at √s = 7 and 8 TeV with the ATLAS and CMS Experiments”, Phys. Lett. 114, 191803 (2015).
4 S. L. Glashow, J. Iliopoulos, and L. Maiani, “Weak interactions with lepton-hadron symmetry”, Phys. Rev. D 2, 1285–1292 (1970).
5 M. Kobayashi and T. Maskawa, “CP-violation in the renormalizable theory of weak interaction”, Progress of Theoretical Physics 49, 652 (1973).
6 J. H. Christenson et al., “Evidence for the 2π decay of the K02 meson”, Phys. Lett. 13, 138–140 (1964).
7 S. W. Herb et al., “Observation of a dimuon resonance at 9.5 GeV in 400-GeV proton-nucleus collisions”,
Phys. Lett. 39, 252–255 (1977).
8 SLD Electroweak Group, DELPHI, ALEPH, SLD, SLD Heavy Flavour Group, OPAL, LEP Electroweak Working Group, L3, “Precision electroweak measurements on the z resonance”, Phys. Rept. 427, 257–454 (2006).
9 “Observation of top quark production in pp collisions with the Collider Detector at Fermilab”, Phys. Lett. 74, 2626–2631 (1995).
10 “Search for high mass top quark production in pp collisions at √s 1.8 TeV”, Phys. Lett. 74, 2422–2426 (1995).
11 Particle Data Group, “Review of particle physics”, Chinese Physics C 40, 100001 (2016).
12 A. Quadt, “Top quark physics at hadron colliders”, Eur. Phys. J. C48, 835–1000 (2006).
13 CDF, “Observation of top quark production in pp collisions”, Phys. Lett. 74, 2626–2631 (1995).
14 D0, “Observation of the top quark”, Phys. Lett. 74, 2632–2637 (1995).
15 H. Georgi et al., “Effects of top quark compositeness”, Phys. Rev. D 51, 3888–3894 (1995).
16 B. Lillie, J. Shu, and T. M. P. Tait, “Top Compositeness at the Tevatron and LHC”, JHEP 04, 087 (2008).
17 A. Pomarol and J. Serra, “Top quark compositeness: feasibility and implications”, Phys. Rev. D 78, 074–026 (2008).
18 K. Kumar, T. M. P. Tait, and R. Vega-Morales, “Manifestations of Top Compositeness at Colliders”, JHEP 05, 022 (2009).
19 U. Baur, M. Spira, and P. M. Zerwas, “Excited-quark and -lepton production at hadron colliders”, Phys. Rev. D 42, 815–824 (1990).
20 R. M. Harris, “Discovery mass reach for excited quarks at hadron colliders”, eConf C960625, NEW164 (1996).
21 W. J. Stirling and E. Vryonidou, “Effect of spin-3/2 top quark excitation on tt ̄ production at the LHC”, JHEP 01, 055 (2012).
22 L. Randall and R. Sundrum, “An alternative to compactification”, Phys. Lett. 83, 4690–4693 (1999).
23 L. Randall and R. Sundrum, “Large mass hierarchy from a small extra dimension”, Phys. Lett. 83, 3370–3373 (1999).
24 B. Hassanain, J. March-Russell, and J. G. Rosa, “On the possibility of light string resonances at the LHC and Tevatron from Randall-Sundrum throats”, JHEP 07, 077 (2009).
25 W. Rarita and J. Schwinger, “On a theory of particles with half-integral spin”, Phys. Rev. 60, 61–61 (1941).
26 CMS, “Search for pair production of excited top quarks in the lepton + jets final state”, JHEP 06, 125 (2014).
27 O. S. Bruning et al., “LHC design report vol.1: the LHC main ring”, (2004).
28 “LHC images”, https://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/lhc_in_pictures.htm (visited on 05/24/2017).
29 CMS Collaboration, “The CMS experiment at the CERN LHC”, JINST 3, S08004 (2008).
30 T. G. Berlincourt and R. R. Hake, “Superconductivity at high magnetic fields”, Phys. Rev. 131, 140–157 (1963).
31 L. Taylor, “Silicon strips”, About CMS - Detector overview (2011).
32 B. Isildak, “Measurement of the differential dijet production cross section in proton-proton collisions at √s= 7 tev”, PhD thesis, (2011).
33 H. Bethe and J. Ashkin, “Passage of radiations through matter”, Experimental Nuclear Physics, 253 (1953).
34 CMS Collaboration, “Commissioning of the CMS high-level trigger with cosmic rays”, JINST 5, T03005 (2010).
35 N. Bernardino Rodrigues et al., “Fast beam conditions monitoring (BCM1F) for CMS”, (2008).
36 A. Kornmayer, “The CMS pixel luminosity telescope”, Nucl. Instrum. Meth. A 824, 304–306 (2016).
37 S. van der Meer, “Calibration of the effective beam height in the ISR”, CERN Technical Report CERN-ISR-PO-68-31, (1968).
38 D. Barney, “CMS detector slice”, CMS Collection, (2016).
39 CMS, “Particle-flow reconstruction and global event description with the CMS detector”, Submitted to JINST., (2017).
40 R. E. Kalman, “A new approach to linear filtering and prediction problems”, Journal of Basic Engineering 82, 35–45 (1960).
41 R. Frühwirth, W. Waltenberger, and P. Vanlaer, “Adaptive vertex fitting”, CMS Notes CMS-NOTE-2007-008, (2007).
42 W. Adam et al., “Reconstruction of electrons with the Gaussian-sum filter in the CMS tracker at the LHC”, tech. rep. CMS-NOTE-2005-001, (2005).
43 M. Cacciari, G. P. Salam, and G. Soyez, “The anti-k(t) jet clustering algorithm”, JHEP 04, 063 (2008).
44 “Determination of jet energy calibration and transverse momentum resolution in CMS”, JINST 6, 11002 (2011).
45 CMS Collaboration, “Performance of CMS muon reconstruction in pp collision events at √s= 7 TeV”, JINST 7, 10002 (2012).
46 CMS Collaboration, “Measuring electron efficiencies at CMS with early data”, CMS Physics Analysis Summary CMS-PAS-EGM-07-001, (2008).
47 CMS Collaboration, “Generic tag and probe tool for measuring efficiency at CMS with early data”, CMS Analysis Notes CMS AN-2009-111, (2009).
48 CMS Collaboration, “Jet Performance in pp Collisions at 7 TeV”, CMS Physics Analysis Summary CMS-PAS-JME-10-003, (2010).
49 N. M.Diamantopoulou and E.Tziaferi, “Performance of the particle-flow jet identification criteria using proton-proton collisions at 13 TeV with the 2015 dataset”, CMS Analysis Notes CMS AN-15-269, (2015).
50 “Jet energy scale and resolution in the CMS experiment in pp collisions at 8 tev”, JINST 12, P02014 (2017).
51 N. Bartosik, “B-jet tagging”, HEP Sketches, (2016).
52 CMS Collaboration, “Identification of b quark jets at the CMS experiment in the LHC Run 2”, CMS Physics Analysis Summary CMS-PAS-BTV-15-001, (2016).
53 “CMS physics: technical design report volume 1: detector performance and software”, Technical Design Report CMS (CERN, Geneva, 2006).
54 A. Buckley et al., “LHAPDF6: parton density access in the LHC precision era”, Eur. Phys. J. C75, 132 (2015).
55 J. Alwall et al., “MadGraph 5: going beyond”, JHEP 2011, 128 (2011).
56 NNPDF, “Parton distributions for the LHC Run II”, JHEP 04, 040 (2015).
57 P. Nason, “A new method for combining NLO QCD with shower Monte Carlo algorithms”, JHEP 11, 040 (2004).
58 S. Frixione, P. Nason, and C. Oleari, “Matching NLO QCD computations with parton shower simulations: the POWHEG method”, JHEP 11, 070 (2007).
59 S. Alioli et al., “A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX”, JHEP 06, 043 (2010).
60 J. M. Campbell et al., “Top-pair production and decay at NLO matched with parton showers”, JHEP 04, 114 (2015).
61 J. Alwall et al., “Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions”, Eur. Phys. J. C53, 473–500 (2008).
62 J. Alwall et al., “The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations”, JHEP 07, 079 (2014).
63 R. Frederix and S. Frixione, “Merging meets matching in MC@NLO”, JHEP 12, 061 (2012).
64 T. Sjöstrand et al., “An introduction to PYTHIA 8.2”, Comput. Phys. Commun. 191, 159–177 (2015).
65 GEANT4, “Geant4—a simulation toolkit”, Nucl. Instrum. Meth. A 506, 250–303 (2003).
66 K. Cranmer, “Kernel estimation in high-energy physics”, Comput. Phys. Commun. 136, 198–207 (2001).
67 B. Silverman, “Density estimation for statistics and data analysis” (1986), p. 48.
68 A. N. Kolmogorov, “Sulla Determinazione Empirica di una Legge di Distribuzione”, Giornale dell’Istituto Italiano degli Attuari 4, 83–91 (1933).
69 G. Marsaglia, W. W. Tsang, and J. Wang, “Evaluating Kolmogorov’s distribution”, Journal of Statistical Software 8, 1–4 (2003).
70 S. S. Wilks, “The large-sample distribution of the likelihood ratio for testing composite hypotheses”, Ann. Math. Statist. 9, 60–62 (1938).
71 G. Cowan et al., “Asymptotic formulae for likelihood-based tests of new physics”, Eur. Phys. J. C71, 1554 (2011).
72 OPAL, DELPHI, LEP Working Group for Higgs boson searches, ALEPH, L3, “Search for the standard model Higgs boson at LEP”, Phys. Lett. B565, 61–75 (2003).
73 CMS, “Identification techniques for highly boosted W bosons that decay into hadrons”, JHEP 12, 017 (2014).
74 CMS Collaboration, “Boosted top jet tagging at CMS”, CMS Physics Analysis Summary CMS-PAS-JME-13-007, (2014).
75 J. Thaler and K. Van Tilburg, “Identifying boosted objects with N-subjettiness”, JHEP 03, 015 (2011).
76 “Search for cp violation in tt production and decay in proton-proton collisions at √s= 8TeV”, JHEP 2017, 101 (2017).
77 H. Jeffreys, “An invariant form for the prior probability in estimation problems”, Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences 186, 453–461 (1946).
78 H. Raiffa and R. Schlaifer, “Applied statistical decision theory.”, Behavioral Science 7, 103–104 (1962).
79 F. E. James, “Statistical methods in experimental physics” (World Scientific, Singapore, 2006).
80 R. Barlow, “Asymmetric statistical errors”, in Statistical Problems in Particle Physics, Astrophysics and Cosmology (2004), pp. 56–59.
QRCODE
 
 
 
 
 
                                                                                                                                                                                                                                                                                                                                                                                                               
第一頁 上一頁 下一頁 最後一頁 top