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

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ε eTL (P ) T 1 eTL ε eTL ε 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 × 10 0 10 20 30 40 50 60 70 80 90 100 PT [MeV] ε eTL ( η ) 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 2 1.5 1 0.5 0 0.5 1 1.5 2 η 3 ε (N ) eTL (vertex) 1 eTL ε ε ( φ ) eTL 1 eTL ε 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 5 10 15 20 25 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Data s = 7 TeV 1 TOP_GRL_G5: 697.871 pb Simulation N(vertex) 0 3 2 1 0 1 2 3 φ [Rad] Figure 5.6: TL efficiency measured from Z → ee events in data (black) and MC (red). 59
Jets in this analysis are reconstructed with the anti-kt algorithm with a radius parameter R = 0.4 [99], starting from energy clusters in the calorimeter reconstructed using the scale established for electromagnetic objects. Jets are then calibrated with MC simulation-based pT- and η-dependent correction factors to restore them to the full hadronic energy scale [100]. Jet quality criteria are applied to reject jets that could not be associated to in-time real energy deposits in the calorimeters. These faulty jets could arise from various sources ranging from temporary hardware issues in the calorimeter, the LHC beam conditions and the showers induced by cosmic-ray muons. Jets are removed if they are within ∆R = 0.2 of a well-identified electron candidate, or within ∆R = 0.4 of a TL candidate. Finally, jets are required to have pT > 25 GeV and |η| < 2.5 (in the following referred to as ‘ID jets’). Momentum Resolution For the case of jets in the MC, a correction on the energy resolution is also applied to match that of the data. This smearing is done before the jet selection. 5.3.5 Missing Transverse Energy A good measurement of E miss T is an important requirement for the successful identification and reconstruction of t¯t events. Mismeasured E miss T no real E miss T is present. The E miss T can significantly enhance backgrounds, like multijets or Drell-Yan, where for this analysis is formed from the negative vector sum of transverse momenta of all jets with pT > 20 GeV and |η| < 2.5. The contribution from cells associated with electron candidates is replaced by the candidates’ calibrated transverse energy. The contribution from all ID muons and other calorimeter clusters, including those not belonging to a reconstructed object, is also included. To suppress backgrounds from Drell-Yan decaying into a pair of muons, where one muon is a TL that is not accounted for in the E miss T reconstruction, the E miss T ID muon, with the pT of the TL if the ∆φ between the E miss T is corrected in events with a TL and an opposite-sign and the TL direction is less than 0.15 and there is no ID lepton within ∆R < 0.05 of the TL (in which case the correction already has been taken care of by the E miss T algorithm). The correction is as follows: Figure 5.7 shows the E miss T E miss x E miss y → E miss x − p TL x , → E miss y − p TL y . (5.1) distribution for Drell-Yan events selected in data, where the effect of this correction can be fully appreciated. In the majority of cases of the 2ID+TL events selected in the data, the 60
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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 .
Page 9 and 10:
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
Page 21 and 22: for strong interactions. Although W
Page 23 and 24: particles. Because of the introduct
Page 25 and 26: which is introduced for mass genera
Page 27 and 28: 2.3 Top Quark The large mass of the
Page 29 and 30: ATLAS Preliminary Data 2011 Channel
Page 31 and 32: as the masses of the quarks involve
Page 33 and 34: LEP HERA Tevatron LHC BR(t → qγ)
Page 35 and 36: to Wtb couplings, where limits on a
Page 37 and 38: tion at the collision point, and F
Page 39 and 40: The positive x-direction is defined
Page 41 and 42: large air-core toroids (one barrel
Page 43 and 44: 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: ε (P ) µ TL T 1 TL µ ε TL µ ε
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 and 96: data, has systematic uncertainties
Page 97 and 98: Jets The jet energy scale (JES) and
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.
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[82] ATLAS Collaboration, Expected
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CERN-THESIS-2012-153 26/07/2012 - CERN Document Server

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