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

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for nominal Pb-Pb ion operation. 3.3 The ATLAS Detector Figure 3.1: The LHC injection complex. Due to the experimental conditions at the LHC, the detectors require fast electronics and sensor elements. High detector granularity, good charged particle momentum resolution, particle identification and large geo- metrical coverage are needed as well. To satisfy such requirements, the ATLAS detector comprises several technologies, each of which has been developed to pursue specific goals. The inner detector is a combination of high-resolution semiconductor pixel (Pixel) and strip (SCT) detectors in its inner part, and transition radiation tracking (TRT) detectors in its outer part. The high granularity lead/liquid-argon (LAr) electro- magnetic (EM) sampling calorimeters have excellent performance in terms of energy and angular resolution, along with electron/photon identification. The hadronic calorimetry is done by an iron/scintillating-tile calorimeter, which provides a good jet and missing energy performance. The calorimeter is surrounded by the muon spectrometer, instrumented with separate trigger and high-precision tracking chambers [64]. The ATLAS detector covers nearly the entire solid angle around the collision point. Its geometry is defined by the direction of the beam, with the z-axis parallel to it, and the x-y plane transverse to it. 25
The positive x-direction is defined as pointing from the interaction point to the center of the LHC ring and the positive y-axis is defined as pointing upwards. The azimuthal angle, φ, is measured around the beam axis, and the polar angle θ is the angle from the beam axis. The pseudorapidity is defined as η ≡ −ln tan(θ/2). The distance between objects 1 and 2 in the pseudorapidity-azimuthal angle space, is defined as ∆R ≡ (φ1 − φ2) 2 + (η1 − η2) 2 . The transverse momentum, pT, is defined as psin θ, where p is the momentum. The transverse energy, ET, is defined as E sin θ, where E is the energy measured in the calorimeter, and θ is the polar angle of the energy deposition. Figure 3.2 shows a cut-away view of the detector, where the layout of the different components can be appreciated. Figure 3.3 displays these components separately. Table 3.2 provides a summary of expected energy-momentum resolution of each component, along with their coverage in η. 3.3.1 Magnet System Figure 3.2: Cut-away view from the ATLAS detector [64]. The ATLAS superconducting magnet system can be seen in Figure 3.3(a). It consists of a thin central solenoid (CS), providing the inner detector with a 2 T axial magnetic field, surrounded by a system of three <strong>26</strong>
Page 1 and 2: CERN-THESIS-2012-153 26/07/2012 c
Page 3 and 4: Abstract A search for flavor-changi
Page 5 and 6: Acknowledgments I first want to tha
Page 7 and 8: Table of Contents List of Tables .
Page 9 and 10: List of Tables 2.1 The fundamental
Page 11 and 12: List of Figures 2.1 The potential V
Page 13 and 14: 5.15 Distributions of the 3ID analy
Page 15 and 16: This thesis is organized as follows
Page 17 and 18: the question whether each neutrino
Page 19 and 20: 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: tion at the collision point, and F
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 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 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.
Page 123 and 124:
[82] ATLAS Collaboration, Expected
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