CERN-THESIS-2012-153 26/07/2012 - CERN Document Server

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TL+ TL Invariant Mass Events / ( 1 ) TL+ TL Invariant Mass 0.05 0.04 0.03 0.02 Events / ( 1 ) 0.01 0.05 0.04 0.03 0.02 ATLAS ∫ Internal 1 L dt = 0.7 fb e/gamma stream alpha = 0.6 ± 1.3 alpha2 = 4.6 ± 4.8 mean = 84.796189 ± 11.001715 mean2 = 79.972112 ± 20.370352 n = 14.7 ± 7.8 n2 = 1.0 ± 2.5 sigma = 4.5 ± 6.7 sigma2 = 11.483791 ± 15.611445 0 50 60 70 80 90 100 110 120 + TL TL invariant mass [GeV] 0.01 ATLAS Internal Z→ee MC (a) alpha = 0.6 ± 1.2 alpha2 = 4.7 ± 4.0 mean = 84.871524 ± 10.497748 mean2 = 79.461944 ± 19.809905 n = 14.298642 ± 11.974132 n2 = 1.0 ± 2.5 sigma = 4.3 ± 6.5 sigma2 = 11.062577 ± 15.373774 0 50 60 70 80 90 100 110 120 + TL TL invariant mass [GeV] (c) TL+ TL Invariant Mass Events / ( 1 ) TL+ TL Invariant Mass 0.1 0.08 0.06 0.04 0.02 0.12 Events / ( 1 ) 0.08 0.06 0.04 0.02 ATLAS ∫ Internal 1 L dt = 0.7 fb muon stream mean = 90.8 ± 4.4 sigma = 4.544099 ± 11.181303 width = 1.915010 ± 11.85<strong>26</strong>23 0 50 60 70 80 90 100 110 120 + TL TL invariant mass [GeV] 0.1 ATLAS Internal Z→µ µ MC (b) mean = 90.9 ± 3.8 sigma = 3.933679 ± 11.185895 width = 1.644606 ± 11.563382 0 50 60 70 80 90 100 110 120 + TL TL invariant mass [GeV] Figure 7.1: Opposite charge TLs invariant mass distributions for collisions data (top) and MC (bottom). All distributions are normalized to unity. The fit for each case is shown in blue. 83 (d)
Jets The jet energy scale (JES) and its uncertainty are derived by combining information from test-beam data, LHC collision data and simulation. Uncertainties associated with the energy scale of light-quark jets and b-jets are studied as a function of the jet transverse momentum and η. For jets within the acceptance, the JES uncertainty varies in the range 4-8% as a function of jet pT and η. This uncertainty has a contribu- tion from pile-up. This pile-up uncertainty, in the central region is 5% for jets with 20 < pT < 50 GeV and 2% for jets with 50 < pT < 100 GeV. For forward jets, the pile-up uncertainty is 7% and 3%, in the respective pT ranges. Additional contributions are considered to account for the flavor composition and the presence of nearby jets uncertainties. The former gives an additional uncertainty of 1.1-2.5% to b-jets with pT > 25 GeV. This uncertainty increases with decreasing momentum. The effect of the jet reconstruction efficiency uncertainty is studied by randomly removing 2% of the jets from the events. The effect of potential jet resolution mis-modelling in the MC is evaluated by additional smearing of the reconstructed jet energies within the uncertainties. In each case, the difference with respect to the nominal is taken as the systematic uncertainty. Missing Transverse Energy The most relevant sources of systematic uncertainties in the E miss T measurement come from the scale and resolution of the objects, the description of the pile-up events, and the impact of hardware failures. All changes applied to electrons, muons and jets are propagated to the E miss T measurement. The uncertainties on the scale and resolution of the objects is propagated into E miss T , assuming a 100% correlation between the uncertainty of the objects and the Emiss T . Uncertainties related to the Emiss T itself are also studied. In particular, the effect of the remaining energy in the calorimeter, not associated with any reconstruction objects (Cell Out), and of low momenta (7 GeV < pT < 20 GeV) jets (Soft-Jet) is studied, as well as the uncertainty due to pile-up. Soft-Jet and Cell Out terms are scaled by their total uncertainty assuming a 100% correlation. A flat 10% uncertainty, correlated with Cell Out and Soft-Jets, is applied to account for the uncertainty due to pile-up. To account for the effects of the dead FEBs in the EM calorimeter, affecting about 42% of the total data used in the analysis, an additional systematic uncertainty, denoted LAr readout problem, is considered. It is evaluated by varying by 20% the thresholds used for removing events with the jets directed at the dead region. 84
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CERN-THESIS-2012-153 26/07/2012 c
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Abstract A search for flavor-changi
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Acknowledgments I first want to tha
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Table of Contents List of Tables .
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List of Tables 2.1 The fundamental
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List of Figures 2.1 The potential V
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5.15 Distributions of the 3ID analy
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This thesis is organized as follows
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the question whether each neutrino
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gauge invariant field strength tens
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for strong interactions. Although W
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particles. Because of the introduct
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which is introduced for mass genera
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2.3 Top Quark The large mass of the
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ATLAS Preliminary Data 2011 Channel
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as the masses of the quarks involve
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LEP HERA Tevatron LHC BR(t → qγ)
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to Wtb couplings, where limits on a
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tion at the collision point, and F
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The positive x-direction is defined
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large air-core toroids (one barrel
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3.3.3 Calorimetry The calorimetry i
Page 45 and 46: of ∼ 1% for the H → γγ and H
Page 47 and 48: esolution of 1 cm×1 ns with digita
Page 49 and 50: Luminosity measurement Accurate det
Page 51 and 52: least one hit on the A-side, at lea
Page 53 and 54: caps. The calorimeter selections ar
Page 55 and 56: ut instead fragment to color neutra
Page 57 and 58: Decays A large fraction of the part
Page 59 and 60: The ALGPEN program with HERWIG show
Page 61 and 62: Normalized to unit / 1.96429 GeV No
Page 63 and 64: Chapter 5 Event Selection 5.1 Intro
Page 65 and 66: Variable Cut pT >20 GeV Type MuID t
Page 67 and 68: Identification efficiency eff id 1
Page 69 and 70: (a) (b) Figure 5.4: Electron identi
Page 71 and 72: ε (P ) µ TL T 1 TL µ ε TL µ ε
Page 73 and 74: Jets in this analysis are reconstru
Page 75 and 76: impact parameter significance of we
Page 77 and 78: event is also discarded. Events wit
Page 79 and 80: event kinematics, however no b-jet
Page 81 and 82: Events / 10 GeV trackleptons / 10
Page 83 and 84: analysis, is 22%. Figure 5.13(a) sh
Page 85 and 86: transverse momentum of the leading
Page 87 and 88: Events / 10 GeV Events / 10 GeV 14
Page 89 and 90: two background sources, diboson and
Page 91 and 92: ID leptons provides three different
Page 93 and 94: 3ID Final Selection ZZ and WZ 9.5
Page 95: data, has systematic uncertainties
Page 99 and 100: the fake prediction was scaled down
Page 101 and 102: two or more, and events with E miss
Page 103 and 104: Source MC Background Luminosity ±
Page 105 and 106: Chapter 8 Limit Evaluation 8.1 Intr
Page 107 and 108: means: Q = L( X,s + b) L( , (8.5)
Page 109 and 110: computed from Equation 8.12 replaci
Page 111 and 112: Chapter 9 Conclusions A search for
Page 113 and 114: There are a total of 666236 γ+jets
Page 115 and 116: Appendix B Backgrounds to the 3ID a
Page 117 and 118: Appendix C Systematic Uncertainties
Page 119 and 120: References [1] J. L. Borges, Tres v
Page 121 and 122: [40] G. Lu, F. Yin, X. Wang and L.
Page 123 and 124: [82] ATLAS Collaboration, Expected
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