In this study, a measurement of the production cross section of Standard Model Z bosons in proton-proton collisions in the decay channel Z to tau tau is performed with data of 1.34 fb-1 - 1.55fb-1 recorded by the ATLAS experiment at the LHC at a center-of-mass energy of 7 TeV. An event selection of the data is applied in order to obtain a sample enriched with Z to tau tau events. After background estimations using data and Monte Carlo (MC) simulations, the fiducial cross sections in the sub-channels Z to tau tau to e tau_h + 3nu and Z to tau tau to mu tau_h + 3nu are measured. Together with the geometrical and kinematical acceptance, A_Z, and the well known tau lepton branching fractions, these results are combined to a total inclusive Z to tau tau cross section. A_Z is obtained from MC studies only, and the combination of the channels is done including statistical and systematical uncertainties using the BLUE method. The result is a measured total inclusive cross section of 914.4 plus minus 14.6(stat) plus minus 95.1(syst) plus minus 33.8(lumi) pb. This is in agreement with theoretical predictions from NNLO calculations of 964 plus minus 48 pb and also with measurements previously performed by the ATLAS and CMS experiments. With the increased amount of data, the statistical uncertainty could be reduced significantly compared to previous measurements. Furthermore, a testbeam analysis is performed to study the operation of the electromagnetic and hadronic endcap calorimeters, EMEC and HEC, and of the forward calorimeter, FCal, in the high particle fluxes expected for the upgraded LHC. The high voltage return currents of the EMEC module are analysed in dependence of the beam intensity. The results are compared to model predictions and simulations to extract the point of critical operation. Overall, the results for the critical beam intensities and the critical high voltage currents are in agreement with the predictions, but the assigned uncertainties are rather large. The general behaviour of the high voltage current in dependence of the beam intensity above the critical intensity could be confirmed very well. The testbeam data show that the EMEC can be operated up to highest LHC luminosities, and that ATLAS conserves its excellent calorimeter performance in this detector area.:Contents List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 List of Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2 Theoretical Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.1 The Standard Model of Particle Physics . . . . . . . . . . . . . . . . . . . . 19 2.1.1 Phenomenological Overview . . . . . . . . . . . . . . . . . . . . . . . 19 2.1.2 Quantum Electrodynamics . . . . . . . . . . . . . . . . . . . . . . . . 21 2.1.3 Electroweak Interaction . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.1.4 Particle Masses and the Higgs Mechanism . . . . . . . . . . . . . . . 24 2.1.5 Quantum Chromo Dynamics . . . . . . . . . . . . . . . . . . . . . . . 27 2.2 Z Boson Production and Decay at the LHC . . . . . . . . . . . . . . . . . . 29 2.3 Event Generation and Simulation . . . . . . . . . . . . . . . . . . . . . . . . 31 2.3.1 The Partonic Process . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2.3.2 Hadronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2.3.3 The Underlying Event . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2.3.4 Detector Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2.4 Cross Section Predictions for Z Boson Production at the LHC . . . . . . . . 34 3 The LHC and the ATLAS Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.1 The Large Hadron Collider . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.2 The ATLAS Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.2.1 The Inner Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 3.2.2 The Electromagnetic Calorimeter . . . . . . . . . . . . . . . . . . . . 42 3.2.3 The Hadronic Calorimeter . . . . . . . . . . . . . . . . . . . . . . . . 47 3.2.4 The Muon Spectrometer . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.2.5 Luminosity Measurement . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.2.6 The Trigger System . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.2.7 Data Taking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4 Testbeam Study of Liquid-Argon Calorimeter Performance at High Rates . . . . 55 4.1 Upgrade Plans of the LHC and the ATLAS Calorimeters . . . . . . . . . . . 55 4.2 Testbeam Parameters and Setup . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.3 The Calorimeter Test Modules . . . . . . . . . . . . . . . . . . . . . . . . . . 58 4.4 Test Module Readout and Signal Degradation . . . . . . . . . . . . . . . . . 58 4.5 Measurement and Analysis of the HV Currents . . . . . . . . . . . . . . . . . 61 4.5.1 Device for Precision HV Current Measurement . . . . . . . . . . . . . 62 4.5.2 Testbeam Data Taking . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.5.3 Analysis of the EMEC Currents . . . . . . . . . . . . . . . . . . . . . 63 4.5.4 Beam Intensity Measurement . . . . . . . . . . . . . . . . . . . . . . 65 4.5.5 Comparison of EMEC Currents to Beam Intensity . . . . . . . . . . . 67 4.5.6 Discussion Considering the Predictions . . . . . . . . . . . . . . . . . 72 4.6 Summary of Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 5 Z → τ τ Cross Section Measurement with 1.34-1.55 fb−1 . . . . . . . . . . . . . . . . . . . . 75 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 5.2 Data and Monte Carlo Samples . . . . . . . . . . . . . . . . . . . . . . . . . 75 5.2.1 Trigger Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 5.2.2 Monte Carlo Simulations . . . . . . . . . . . . . . . . . . . . . . . . . 76 5.2.3 Pile-up Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5.2.4 Tau Trigger Weighting . . . . . . . . . . . . . . . . . . . . . . . . . . 78 5.3 Event Preselection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 5.3.1 Good Run List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 5.3.2 Vertex Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 5.3.3 Calorimeter Jet Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . 80 5.3.4 Liquid-Argon Calorimeter Hole Cleaning . . . . . . . . . . . . . . . . 80 5.4 Reconstructed Physics Objects . . . . . . . . . . . . . . . . . . . . . . . . . . 81 5.4.1 Muons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 5.4.2 Electrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 5.4.3 Jets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 5.4.4 Taus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 5.4.5 Missing Transverse Energy . . . . . . . . . . . . . . . . . . . . . . . . 86 5.4.6 Overlap Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 5.5 Event Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.5.1 Dilepton Veto . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.5.2 Opposite Charge Between the Lepton and the Hadronic Tau Candidate 89 5.5.3 Reduction of W+jets Background . . . . . . . . . . . . . . . . . . . . 89 5.5.4 Final Requirements on the Tau Candidate . . . . . . . . . . . . . . . 90 5.5.5 Visible Mass Window . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 5.5.6 Summary of the Event Selection . . . . . . . . . . . . . . . . . . . . . 92 5.6 Tau Identification Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 5.7 Background Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 5.7.1 W+jets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 5.7.2 Z+jets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 5.7.3 QCD Multijet Events . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 5.8 Cross Section Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 5.9 Systematic Uncertainties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 5.9.1 Trigger Efficiencies and Scale Factors . . . . . . . . . . . . . . . . . . 106 5.9.2 Reconstruction, Identification and Isolation Efficiencies of the Muons and Electrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 5.9.3 Identification Efficiency of the Hadronically Decaying Tau . . . . . . 108 5.9.4 Background Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . 109 5.9.5 Geometrical and Kinematical Acceptance AZ . . . . . . . . . . . . . 110 5.9.6 Energy Scale Uncertainty . . . . . . . . . . . . . . . . . . . . . . . . 111 5.9.7 Further Systematic Uncertainties . . . . . . . . . . . . . . . . . . . . 112 5.9.8 Summary of Systematic Uncertainties . . . . . . . . . . . . . . . . . . 112 5.10 Combination of the Channels and Results . . . . . . . . . . . . . . . . . . . 112 5.11 The Z → τ τ Cross Section Measurement in the LHC Physics Context . . . . 115 6 Summary and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 A Gauge Invariance in Quantum Electrodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 A.1 Local gauge invariance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 A.2 Gauge invariance of the Maxwell-Equations . . . . . . . . . . . . . . . . . . . 123 B Testbeam Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 C Tau Trigger Weighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 C.1 Event Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 C.2 Tau Trigger Efficiency Measurement . . . . . . . . . . . . . . . . . . . . . . . 132 C.3 Systematic Uncertainties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 Bibliography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 / In dieser Studie wird eine Wirkungsquerschnittsmessung des Standardmodell-Z-Bosons im Zerfallskanal Z nach tau tau mit Kollisionsereignissen entsprechend 1.34 fb-1 bis 1.55 fb-1 aufgezeichneter Daten des ATLAS-Experiments am LHC bei einer Schwerpunktsenergie von 7 TeV durchgefuehrt. Hierbei kommt eine spezielle Ereignisselektion der Daten zum Einsatz, die zum Ziel hat, einen mit Z nach tau tau Ereignissen angereicherten Datensatz zu erhalten. Nach einer Untergrundabschaetzung mit Hilfe von experimentellen Daten und Monte-Carlo(MC)-Simulationen wird eine spezifische Wirkungsquerschnittsmessung in den Unterkanaelen Z nach tau tau nach e tau_h + 3nu und Z nach tau tau nach mu tau_h + 3nu erreicht, welche zunaechst nur Ereignisse in der geometrischen und kinematischen Akzeptanzregion umfasst. Zusammen mit der Selektionseffizienz dieser Akzeptanzregion, A_Z, und den bekannten Tau-Lepton-Verzweigungsverhaeltnissen koennen diese Ergebnisse zu einem totalen, inklusiven Z nach tau tau Wirkungsquerschnitt kombiniert werden. Hierbei wird A_Z ausschliesslich aus MC-Studien bestimmt und die Kombination unter Beruecksichtigung der statistischen und systematischen Fehler der Einzelkanaele mit der BLUE-Methode durchgefuehrt. Das Ergebnis ist ein totaler, inklusiver Wirkungsquerschnitt von 914.4 plus minus 14.6(stat) plus minus 95.1(syst) plus minus 33.8(lumi) pb. Dies stimmt innerhalb der Messunsicherheiten sowohl mit theoretischen Vorhersagen aus NNLO Rechnungen von: 964 plus minus 48 pb als auch mit Messungen, die zuvor im Zuge der ATLAS- und CMS-Experimente durchgefuehrt wurden, ueberein. Im Vergleich zu den bisherigen Messungen koennen die statistischen Fehler mit dem groesseren Datensatz deutlich reduziert werden. Weiterhin wird eine Teststrahlstudie zur Pruefung der Funktionalitaet der elektromagnetischen und hadronischen Endkappenkalorimeter, EMEC und HEC, und des Vorwaertskalorimeters FCal in den zukuenftigen, hohen Teilchenflussdichten des verbesserten LHC praesentiert. Die Hochspannungsstroeme des EMEC-Moduls werden in Abhaengigkeit von der Strahlintensitaet analysiert. Weiterhin werden die Ergebnisse mit Modellvorhersagen und Simulationen verglichen, um die Punkte nichtlinearen (kritischen) Betriebes zu extrahieren. Die Ergebnisse fuer die kritische Strahlintensitaet und die kritischen Stroeme stimmen mit Modellrechnungen und Simulationen ueberein, die jedoch mit grossen Unsicherheiten behaftet sind. Das vorhergesagte Verhalten der Hochspannungsstroeme in Abhaengigkeit von der Strahlintensitaet oberhalb der kritischen Intensitaet konnte sehr genau bestaetigt werden. Die Teststrahldaten zeigen, dass das EMEC bis zu den hoechsten LHC-Luminositaeten arbeiten kann und ATLAS in dieser Detektorregion seine exzellenten Kalorimetereigenschaften beibehaelt.:Contents List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 List of Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2 Theoretical Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.1 The Standard Model of Particle Physics . . . . . . . . . . . . . . . . . . . . 19 2.1.1 Phenomenological Overview . . . . . . . . . . . . . . . . . . . . . . . 19 2.1.2 Quantum Electrodynamics . . . . . . . . . . . . . . . . . . . . . . . . 21 2.1.3 Electroweak Interaction . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.1.4 Particle Masses and the Higgs Mechanism . . . . . . . . . . . . . . . 24 2.1.5 Quantum Chromo Dynamics . . . . . . . . . . . . . . . . . . . . . . . 27 2.2 Z Boson Production and Decay at the LHC . . . . . . . . . . . . . . . . . . 29 2.3 Event Generation and Simulation . . . . . . . . . . . . . . . . . . . . . . . . 31 2.3.1 The Partonic Process . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2.3.2 Hadronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2.3.3 The Underlying Event . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2.3.4 Detector Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2.4 Cross Section Predictions for Z Boson Production at the LHC . . . . . . . . 34 3 The LHC and the ATLAS Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.1 The Large Hadron Collider . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.2 The ATLAS Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.2.1 The Inner Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 3.2.2 The Electromagnetic Calorimeter . . . . . . . . . . . . . . . . . . . . 42 3.2.3 The Hadronic Calorimeter . . . . . . . . . . . . . . . . . . . . . . . . 47 3.2.4 The Muon Spectrometer . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.2.5 Luminosity Measurement . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.2.6 The Trigger System . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.2.7 Data Taking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4 Testbeam Study of Liquid-Argon Calorimeter Performance at High Rates . . . . 55 4.1 Upgrade Plans of the LHC and the ATLAS Calorimeters . . . . . . . . . . . 55 4.2 Testbeam Parameters and Setup . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.3 The Calorimeter Test Modules . . . . . . . . . . . . . . . . . . . . . . . . . . 58 4.4 Test Module Readout and Signal Degradation . . . . . . . . . . . . . . . . . 58 4.5 Measurement and Analysis of the HV Currents . . . . . . . . . . . . . . . . . 61 4.5.1 Device for Precision HV Current Measurement . . . . . . . . . . . . . 62 4.5.2 Testbeam Data Taking . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.5.3 Analysis of the EMEC Currents . . . . . . . . . . . . . . . . . . . . . 63 4.5.4 Beam Intensity Measurement . . . . . . . . . . . . . . . . . . . . . . 65 4.5.5 Comparison of EMEC Currents to Beam Intensity . . . . . . . . . . . 67 4.5.6 Discussion Considering the Predictions . . . . . . . . . . . . . . . . . 72 4.6 Summary of Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 5 Z → τ τ Cross Section Measurement with 1.34-1.55 fb−1 . . . . . . . . . . . . . . . . . . . . 75 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 5.2 Data and Monte Carlo Samples . . . . . . . . . . . . . . . . . . . . . . . . . 75 5.2.1 Trigger Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 5.2.2 Monte Carlo Simulations . . . . . . . . . . . . . . . . . . . . . . . . . 76 5.2.3 Pile-up Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5.2.4 Tau Trigger Weighting . . . . . . . . . . . . . . . . . . . . . . . . . . 78 5.3 Event Preselection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 5.3.1 Good Run List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 5.3.2 Vertex Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 5.3.3 Calorimeter Jet Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . 80 5.3.4 Liquid-Argon Calorimeter Hole Cleaning . . . . . . . . . . . . . . . . 80 5.4 Reconstructed Physics Objects . . . . . . . . . . . . . . . . . . . . . . . . . . 81 5.4.1 Muons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 5.4.2 Electrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 5.4.3 Jets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 5.4.4 Taus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 5.4.5 Missing Transverse Energy . . . . . . . . . . . . . . . . . . . . . . . . 86 5.4.6 Overlap Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 5.5 Event Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.5.1 Dilepton Veto . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 5.5.2 Opposite Charge Between the Lepton and the Hadronic Tau Candidate 89 5.5.3 Reduction of W+jets Background . . . . . . . . . . . . . . . . . . . . 89 5.5.4 Final Requirements on the Tau Candidate . . . . . . . . . . . . . . . 90 5.5.5 Visible Mass Window . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 5.5.6 Summary of the Event Selection . . . . . . . . . . . . . . . . . . . . . 92 5.6 Tau Identification Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 5.7 Background Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 5.7.1 W+jets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 5.7.2 Z+jets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 5.7.3 QCD Multijet Events . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 5.8 Cross Section Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 5.9 Systematic Uncertainties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 5.9.1 Trigger Efficiencies and Scale Factors . . . . . . . . . . . . . . . . . . 106 5.9.2 Reconstruction, Identification and Isolation Efficiencies of the Muons and Electrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 5.9.3 Identification Efficiency of the Hadronically Decaying Tau . . . . . . 108 5.9.4 Background Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . 109 5.9.5 Geometrical and Kinematical Acceptance AZ . . . . . . . . . . . . . 110 5.9.6 Energy Scale Uncertainty . . . . . . . . . . . . . . . . . . . . . . . . 111 5.9.7 Further Systematic Uncertainties . . . . . . . . . . . . . . . . . . . . 112 5.9.8 Summary of Systematic Uncertainties . . . . . . . . . . . . . . . . . . 112 5.10 Combination of the Channels and Results . . . . . . . . . . . . . . . . . . . 112 5.11 The Z → τ τ Cross Section Measurement in the LHC Physics Context . . . . 115 6 Summary and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 A Gauge Invariance in Quantum Electrodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 A.1 Local gauge invariance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 A.2 Gauge invariance of the Maxwell-Equations . . . . . . . . . . . . . . . . . . . 123 B Testbeam Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 C Tau Trigger Weighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 C.1 Event Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 C.2 Tau Trigger Efficiency Measurement . . . . . . . . . . . . . . . . . . . . . . . 132 C.3 Systematic Uncertainties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 Bibliography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

Perovskite-based photovoltaic is one of the most promising classes of emerging solar cell technologies. This material class combines several advantageous properties, including low exciton binding energy, high charge carrier diffusion length and high optical absorption. Despite these excellent attributes, some challenges remain in perovskite research. Most notably the device stabilities and lifetimes need to be significantly improved in order to push this technology towards commercialization. Defect physics in perovskite photovoltaics has been shown to be a main factor in understanding long-term device instabilities. However, the number of measurement techniques that can track changes in the ionic landscape during device degradation is very limited, as the perovskite layer is buried under charge extraction layers and metallic contacts. In this thesis argon gas-cluster ion beam etching is combined with x-ray and ultraviolet photoelectron spectroscopy to achieve high resolution energetic and compositional depth profiles. In contrast to most layer-to-layer techniques this method can be applied after any operation time of the photovoltaic and therefore nicely investigate potential changes in the defect landscape. In the first part of this thesis, the impact of argon gas-cluster etching on the perovskite structure is investigated in order to identify potential damage that prevents this technique from being viable for perovskite materials. It is found that metallic lead is gradually created and a small preferential etching effect of the organic cations takes place during the depth profiling, but it is demonstrated that the major part of the crystal structure stays intact and that the energetics of the sample remains very stable. Moreover, it is demonstrated that fitting of the obtained ultraviolet photoelectron spectroscopy spectra leads to high resolution energetic and compositional depth profiles, which are suitable to identify potential loss mechanisms in full photovoltaic devices. In the second part, we investigate the increase in device performance of a perovskite photovoltaic during the first subsequent measurements under full illumination, which is a common example of a short-term instability. Ultraviolet photoelectron spectroscopy depth profiles reveal a strong band bending effect appearing after biasing the device which consequently leads to an increase in device open-circuit voltage. Density functional theory simulations link this band bending effect to the accumulation of iodine interstitials at the interface between the perovskite and the electron transport layer. In the final part, long-term degradation of perovskite photovoltaics is studied by investigating the impact of ionic additives on the perovskite active layer, which increases the lifetime of these devices significantly. It is found that most properties of the perovskite layer remain unaffected by the ionic additive, e.g. microstructure, energetic disorder and photoluminescence. Photoelectron spectroscopy depth profiling revealed an accumulation of iodine at the interface towards the electron transport layer, which is significantly reduced in additive-containing samples. Deep-level transient spectroscopy revealed a new mobile defect species in the ionic additive samples and at the same time a reduction of iodine diffusivity.

Die laufenden Aufrüstungsarbeiten des Large Hadron Colliders haben das Ziel, die Luminosität der Teilchenkollisionen zu erhöhen. Die erhöhte Luminosität liefert zwar neue Möglichkeiten für Präzisionsmessungen und Teilchensuchen, stellt aber gleichzeitig eine große Herausforderung an die beteiligten Experimente. Aus diesem Grund wird auch der ATLAS-Detektor aufgerüstet. Der Fokus ist dabei, eine hohe Effizienz des Triggers sicherzustellen, der die interessanten Physikereignisse in Echtzeit auswählt. Dafür wird das Flüssig-Argon-Kalorimeter des ATLAS-Detektors mit einer neuen Ausleseelektronik ausgerüstet. Um die Funktionsfähigkeit zu testen, wurde ein Demonstrationsaufbau der zukünftigen Ausleseelektronik installiert und von 2014 bis 2018 parallel zur ATLAS- Datennahme betrieben. In dieser Arbeit werden die Daten, die mit dem Aufbau aufgezeichnet wurden, analysiert. Die neue Ausleseelektronik erlaubt es, komplexere Algorithmen zur Erkennung von Signal- und Untergrundereignissen zu nutzen. Es handelt sich dabei um Variablen zur Beschreibung der Form von elektromagnetischen und hadronischen Teilchenschauern im Flüssig-Argon-Kalorimeter. Die Effizienz dieser Variablen wird untersucht. Dabei wird nach Kombination mehrerer Variablen eine Untergrundunterdrückung hadronischer Jets von 75 % bei einer Elektronenerkennungseffizienz von 90 % erreicht. Die zukünftige, erhöhte Luminosität führt dazu, dass sich bei Teilchenkollisionen die Zahl der Ereignisse, die sich sowohl zeitlich als auch räumlich überlappen, erhöht. Der Effekt dieser Überlappereignisse hat Auswirkungen auf die Energierekonstruktion. Daher wird eine Untersuchung der Überlappereignisse durchgeführt, um eine möglichst genaue Kenntnis über diese zu erhalten. Für die Rekonstruktion aus den Signalen der im Detektor deponierten Energie stehen verschiedene digitale Signalfilter zur Auswahl. Die Performanz hinsichtlich der Signalerkennung dieser Algorithmen wird überprüft. Es zeigt sich, dass neue digitale Signalfilter zwar den Effekt des zeitlichen Überlapps von Detektorpulsen reduzieren, jedoch sehr sensitiv auf die genaue Pulsmodellierung sind. / The ongoing upgrade activities at the Large Hadron Collider aim for an increase of the luminosity in the particle collisions. The increased luminosity delivers new capabilities for precision measurements and searches for signatures of new physics. At the same time, challenges arise for the experiments. For this reason, the ATLAS detector is upgraded. The focus is on maintaining the high efficiency of the trigger that selects interesting physics events in real-time. Therefore, the Liquid-Argon calorimeter of the ATLAS detector is upgraded with new readout electronics. To evaluate the performance, a demonstrator readout was installed and operated in parallel to the data taking of the main readout between 2014 and 2018. In this thesis, the data recorded with the demonstrator is analyzed. The new readout electronics allow more sophisticated algorithms to distinguish between signal and background events. They are based on variables that describe electromagnetic and hadronic showers. The proposed shower-shape variables are studied concerning their trigger efficiency and background rejection power. With a combination of the shower-shape variables, a background rejection power of 75 % for hadronic jets is achieved while keeping the electron trigger efficiency at 90 %. The increase in luminosity will lead to an increase in in-time and out-of-time pile-up effects. These have an impact on the energy reconstruction. Therefore, pile-up events are investigated, to gain precise knowledge about their effects. For the energy reconstruction of the detector signals, different digital filter algorithms are available. The signal detection efficiency of these algorithms is examined. While new filter algorithms are capable of reducing the effect of out-of-time pile-up, they depend greatly on the correct phase of the pulse shape.

This thesis presents experimental studies of various non-thermal atmospheric pressure gas discharges generated using short pulsed excitation as an alternative to widely used sinusoidal excitation. Several pulse generators are detailed that provide high voltage pulses ranging from hundreds of microseconds to less than ten nanoseconds in duration. A key enabler to the generation of a stable discharge is a suitably high repetition rate; this prerequisite precludes many conventional pulsed power technologies. Fortunately, recent advances in semiconductor technology have made it possible to construct solid state switches capable of producing high voltage pulses with repetition rates of many kilohertz. Pulsed excitation introduces many opportunities to tailor the applied voltage and consequently enhance the discharge which are not possible with sinusoidal excitation sources. Through detailed electrical and optical analysis it is shown that pulsed excitation is not only more energy efficient than a comparable sinusoidal source but produces a higher flux of excited species that are essential in many applications. When pulse widths are reduced to a sub-microsecond timescale a novel barrier-free mode of operation is observed. It is shown that diffuse large area plasmas are easily produced at kilohertz repetition rates without the usually indispensable dielectric barriers. Experimental results show that a short pulse width prevents the onset of the undesirable glow-to-arc transition thus introducing an added degree of stability. A further benefit of pulsed excitation is the ability to produce gas discharges with a high instantaneous peak power yet low average power consumption, resulting in a high density plasma that exhibits roomtemperature characteristics. Finally, as an acid test to highlight the many benefits of pulsed excitation several real-world applications are considered. It is shown that in all cases pulsed gas discharges provide real benefits compared to their sinusoidal counterparts.

Scanning electron microscopy of Ar-ion milled samples from the Eagle Ford Formation, South Texas shows that the character and abundance of porosity changes significantly across burial conditions as a result of compaction, cementation, bitumen generation, and generation of secondary porosity within organic matter (OM). Samples displaying a range of compositions and maturities are imaged and quantified to provide insight into the effects of these processes. Porosity in low-maturity samples (Ro~0.5%) is volumetrically dominated (0.1% -12.5% bulk volume, average 6.2%) by relatively large, mostly interparticle, primary mineral-associated pores (median sizes range 35.9-52.7 nm). Larger pores are generally associated with coccolith debris that is commonly aggregated into pellets. Porosity and pore size correlate directly with calcite abundance and inversely with OM volumes. OM is dominantly detrital kerogen "stringers" that range in size and have spatial distributions and character suggestive of detrital origin. Destruction of primary porosity in low-maturity samples has occurred due to compaction of ductile kerogen and clays and, to a minor degree, as a result of cementation and infill of early bitumen. Smaller, secondary OM-hosted pores (median size range 11.1-14.9 nm) volumetrically dominate porosity (0.02%-3.6% bulk volume, average of 1.36%), in most high-maturity samples (Ro~1.2%-1.3%). Mineral-associated pores are present, but are typically smaller (median size range from 20.3-40.6 nm) and less abundant (0.0%-10.0% bulk volume, average of 2.5%) than at low maturity. Abundant mineral-associated porosity is present locally in samples where incursion of primary pore space by bitumen has not occurred. OM within high-maturity samples is distributed more evenly throughout the rock fabric, occupying spaces similar in size and morphology to primary interparticle pores, coating euhedral crystals (probable cements), and filling intraparticle porosity. These observations, and positive correlation between calcite and OM volumes (OM-hosted pore volume included) in samples with dominantly OM-hosted pore networks, suggests that a large portion of OM within high-maturity samples is diagenetic in origin and has filled primary pore space. Destruction of primary porosity in high-maturity samples has occurred through cementation, bitumen infill, and, possibly greater compaction. Additional porosity, however, has been generated through maturation of OM. / text

Dans le cadre d'un projet sur un procédé de projection de cuivre sur des matériaux composites par torche plasma, l'objectif de ce travail est de calculer les propriétés radiatives et de transport pour un mélange Ar/H2/Cu, pour des températures comprises entre 300K et 25000K, et à la pression atmosphérique. En supposant l'ETL, le calcul préalable de la composition permet de déterminer les coefficients de transport et les propriétés radiatives suivant trois méthodes :<br /><br />- le coefficient d'émission nette pour un milieu homogène et isotherme constituant une assez bonne approximation du rayonnement émis par les régions les plus chaudes. <br /><br />- le ‘coefficient moyen d'absorption' basé sur un découpage préliminaire de l'ensemble du spectre en quelques intervalles, la valeur du coefficient d'absorption étant supposée constante dans chacun d'eux pour une température donnée. Cette méthode est intéressante pour trois raisons : sa cohérence avec les valeurs du coefficient d'émission nette dans les régions chaudes ; le calcul explicite de l'absorption du rayonnement dans les régions tièdes du plasma ou dans le gaz froid environnant ; l'utilisation de ces données dans des codes de calcul de mécanique des fluides appliqués aux plasmas thermiques. <br /><br />- la méthode de Chapman-Enskog utilisée pour déterminer les coefficients de transport et basée sur la résolution de l'équation intégro-différentielle de Boltzmann. Une étude critique des intégrales de collision a permis de sélectionner un jeu cohérent de valeurs permettant le calcul original des coefficients de transport pour notre mélange ternaire. <br /><br />Enfin, une étude expérimentale du jet de plasma a été également menée dans le cadre de cette thèse. A partir de méthodes de diagnostics par spectroscopie d'émission, le principal objectif consiste à caractériser l'état d'un plasma Ar/H2 en présence de cuivre et à déterminer les paramètres fondamentaux de la décharge (température, densités des diverses espèces).

No description available.

O objetivo deste trabalho foi investigar a variação do comprimento de onda na fotoativação de resina composta com Laser de argônio, por meio, dos testes de microdureza Vickres, variação de temperatura durante o processo de polimerização, grau de conversão e ablação. Os experimentos de microdureza foram conduzidos utilizando o aparelho MMT-3 Hardness Tester (Buehler Lake Bluff, IlIinois USA) equipado com diamante Vickers. Para medir a temperatura foi utilizado um termistor de alta precisão conectado a multímetro onde foram medidos valores de resistência em (Ohm). Para medir o grau de conversão utilizou-se o Espectrofotômetro FTIR BOMEM, modelo MB-102, na faixa espectral de 4000 a 400 cm-1. As amostras foram ablacionadas com o laser de Er:YAG pulsado, no regime de microssegundos, após a ablação os diâmetros e profundidades foram medidos com uma lupa com aumento de 40X e um relógio comparador. As amostras foram ablacionadas com Laser Libra-S (Coherent, Pala Alto, CA, EUA), no regime de femtossegundos, e medidos os diâmetros das microcavidades por meio de uma imagem gerada pelo microscópio eletrônico de varredura MEV (DSM 960, Zeiss, Jena, Germany). As imagens foram processadas em um programa matemático, onde foram calculados os diâmetros e com isso, calculada a intensidade threshold de ablação. As amostras foram confeccionadas em resina composta do tipo microhíbrida Z-250 (3M-Espe) fotoativada com o laser de argônio (Coherent, Innova 200-20, USA). Foram utilizados os comprimentos de ondas de 476.5,488.0, 501.7 e 514 nm, com tempos de exposições de 15, 40, 60, 300, 900 segundos. Considerando os testes realizados o melhor comprimento de onda para a fotoativação foi 488.0 nm, conforme pôde ser visto nos experimentos abordados nessa dissertação. / The aims this work to investigate the variation of the wavelength in the photoactivation of composite resin with argon, by means, them tests of microhardness Vikres, variation of temperature during the polymerization process, degree of conversion and ablation. The microhardness experiments were lead using device MMT-3 Microhardness Tester (Buehler Lake Bluff, Illinois the USA) equipped with Vickers diamond. To measure the temperature rise the multimeter was used a thermister of high precision hardwired where values of resistance in (Ohm) were measured. To the degree of conversion was used Spectrophotometer FTIR BOMEM, model MB-102, in the spectral band of 4000 to 400cm-1. The samples were ablateds with the Er:YAG Laser, in the regimen of microseconds, the ablation the diameter and depth has been after measured with a magnifying glass with increase of 40X and comparing a clock. The sample were ablated with Libra-S Laser (Coherent, High Palo, CA, U.S.A.), in the regiment femtosecond, and measured the diameter of the microcavities, by means, of a image generated for the electron microscope of sweepings SEM (DSM 960, Zeiss, Jena, Germany). The images were processed in a mathematical program, where the diameters were calculated and with this, calculated the threshold intensity of ablation. The samples had been confectioned in composed resin of the photo-activad Z-250 (3M-ESPE) microhibrid type with the argon laser (Coherent, Innova 200-20, the USA). The wavelength of 476.5, 488.0, 501.7 and 514.5 nm were used, with exposure times of 15, 40, 60, 300, 900 seconds. Considering the five carried through tests optimum wavelength for the photo-activation was 488.0 nm, o it could be in the boarded experiment in this dissertation.

O objetivo do estudo foi avaliar o efeito da utilização de película de metilcelulose e das atmosferas de acondicionamento com ar atmosférico, vácuo e argônio sobre a conservação de batatas minimamente processadas (MP) e também sobre sua qualidade após fritura. Tubérculos foram selecionados, lavados, sanificados, cortados na forma de palitos e tratados com ácido cítrico. As batatas foram imersas em solução filmogênica contendo metilcelulose (1%) e sorbitol (0,75%) como plastificante, com posterior secagem, acondicionadas sob ar atmosférico, e modificada com argônio (20seg. e 230mmHg), além de vácuo (15seg. e 54mmHg). O produto MP armazenado a 8°C durante 12 dias foi avaliado em intervalos de 3 dias mediante análises microbiológicas, fisiológicas, físicoquímicas e físicas. A cada 3 dias as batatas MP foram também fritas e avaliadas quanto à perda de umidade, absorção de óleo, textura instrumental e avaliação sensorial. O acondicionamento sob ar atmosférico foi efetivo em reduzir a perda de massa das batatas MP. As embalagens sob vácuo foram mais efetivas para o produto MP sem película, pois mantiveram o pH, acidez titulável, teor de amido e de açúcares mais próximos do dia do início do experimento, como também mantiveram baixo o índice de escurecimento. O acondicionamento sob vácuo, entretanto, não seria indicado quando a finalidade fosse a fritura, pois foi o tratamento que apresentou maiores perdas de umidade e maior absorção de óleo. O acondicionamento sob atmosfera de argônio também foi mais efetivo nas batatas MP sem película, sendo fator determinante em reduzir os teores de CO2 no interior da embalagem, apresentou menor taxa respiratória, menor índice de escurecimento tanto antes como após a fritura, reduziu a perda de umidade durante a fritura, manteve mais a firmeza do produto frito e também minimizou a absorção de óleo a partir do 3° dia de armazename nto. A utilização de película foi efetiva em reduzir a respiração do produto MP até o 6° dia. Já no produto frito, foi fator determinante na retenção de umidade das batatas, como também na redução, ao longo do armazenamento, da absorção de óleo / The aim of this study was to evaluate the effect of methylcellulose as edible coating and packaging atmospheres with atmospheric air, vacuum and argon on the conservation of minimally processed (MP) potatoes as well as on their quality after frying. Tubers were selected, washed, sanitized, cut in the shape of sticks and treated with citric acid. Potatoes were immersed in a filmogenic solution of methylcellulose (1%) with sorbitol (0,75%) as a plasticizer, dehydrated, and then packaged under atmospheric air, and modified with argon (20seg. e 230mmHg), and vacuum (15seg. e 54mmHg). Stored MP product at 8°C for 12 days was assessed at intervals of 3 days by microbiological, physiological, physicochemical and physical analyses. Every 3 days the MP potatoes were fried and evaluated for moisture loss, oil absorption, instrumental texture and sensory evaluation. Packaging under atmospheric air was effective in reducing the mass loss of MP potatoes. The vacuum packaging was more effective for the MP product without edible coating, because they kept the pH, acidity, starch and sugar level more similar to the first day experiment, as well as low browning rate. The vacuum packaging, however, would not be appropriate when the purpose is frying, because this treatment showed the greatest loss of moisture and increased oil absorption. Packaging under argon atmosphere was also more effective for the MP product without edible coating, and it was an important factor to reduce CO2 levels inside the package, showed lower respiratory rate, lower browning index both before and after frying, reduced moisture loss during frying, kept fried product firmness better and also minimized oil absorption from the 3rd day of storage. The use of edible coating was effective in reducing the respiration of MP product until the 6rd day. For the fried product, the use of coating was a determining factor for moisture retention during frying of potatoes, and also to decrease oil absorption along the potato storage.

Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2014-07-31T12:16:56Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Calculo_da_condutividade_termica_do_argonio_solido_puro_e_com_defeito_pontual.pdf: 283748 bytes, checksum: d7815053104cf5341740be05c829feff (MD5) / Made available in DSpace on 2014-07-31T12:16:57Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Calculo_da_condutividade_termica_do_argonio_solido_puro_e_com_defeito_pontual.pdf: 283748 bytes, checksum: d7815053104cf5341740be05c829feff (MD5) Previous issue date: 2008-03-14 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work, using the Green-Kubo method combined with Molecular Dynamic (DM), we calculate the thermal conductivity of a solid Argon "free of defects"and with point defect present, for temperatures varying from 10 up to 60 K at density 22,3 ml/mol. The obtained results are in good agreement with the available theoretical and experimental results in the limites of low and high temperatures, but with some discrepances in about 15 % for intermediate values of temperatures. The purpose to include point defects with the objective of correction of the simulational results to compare with experimental measuremments for intermediate temperatues had not the expected e?ect. However, we believe that it should be due to the fact that the density used in the simulation for the point defect is high based on the experimental estimates of point defect density in this system. Our results suggest that the Green-Kubo method combined with Molecular Dynamics is a powerful tool to calculate the thermal conductivity of solids at high temperatures. With the construction of accurate and reliable interatomic potentials to describe more complex materials, such as high temperature ceramic and minerals at extreme condiction of pressure and temperature, this method could soon become very useful to calculate thermal conductivity in materials where the access to experimental data is hard. / Neste trabalho, usando o método de Green-Kubo combinado com a Dinâmica Molecular (DM), calculamos a condutividade têrmica do Argônio sólido livre de defeitos ;e com defeitos pontuais presentes, para um intervalo de temperatura variando de 10 a 60 K e uma densidade de 22,3 ml/mol. Os resultados obtidos estão em pleno acordo com os resultados teóricos e experimentais disponíveis nos limites de baixa e alta temperatura, mas com alguma discrepância em torno de 15 % para valores intermediários de temperatura. A proposta para incluir defeitos pontuais com o objetivo de correção dos resultados da simulação para comparar com as medidas experimentais para temperaturas intermediárias não surtiu o efeito esperado, no entanto, acreditamos que isto se deve ao fato da densidade de defeitos ser alta baseado em estimativas da densidade de defeitos neste sistema. Nossos resultados sugerem que o método de Green-Kubo combinado com DM é uma ferramenta poderosa para se calcular a condutividade térmica de sólidos a altas temperaturas. Com a construção de potenciais interatômicos mais precisos e con fiáveis para descrever materiais mais complexos, como é o caso de cerâmicas a altas temperaturas e minerais em condições extrema de pressão e temperatura, esse método poderá em breve ser muito útil para calcular a condutividade térmica em materiais onde o acesso a dados experimentais é mais difícil.