The Gas Electron Multiplier (GEM) upgrade project aims at improving the performance of the muon spectrometer of the Compact Muon Solenoid (CMS) experiment which will suffer from the increase in luminosity of the Large Hadron Collider (LHC). After a long technical stop in 2019-2020, the LHC will restart and run at a luminosity of 2 10^34 cm^-2 s^-1, twice its nominal value. This will in turn increase the rate of particles to which detectors in CMS will be exposed and affect their performance. The muon spectrometer in particular will suffer from a degraded detection efficiency due to the lack of redundancy in its most forward region. To solve this issue, the GEM collaboration proposes to instrument the first muon station with Triple-GEM detectors, a technology which has proven to be resistant to high fluxes of particles. Within the GEM collaboration, the Data Acquisition (DAQ) subgroup is in charge of the development of the electronics and software of the DAQ system of the detectors.This thesis presents the work of the author as lead developer of the firmware for the front-end and back-end electronics. These developments have been performed from the ground up and designed to transfer data from the analog front-end to the off-detector electronics while offering extensive control and monitoring capabilities. The developed DAQ chain has been tested extensively during two test beam campaigns which provided results on both the stability of the system and the efficiency of the detectors. The results of these campaigns are described in the present thesis. Further characterization of the electronics is also described along with the procedures and tools built to qualify the components for their installation in CMS. Finally, the results of the irradiation tests performed on the on-detector electronics are presented. These allowed us to understand the effects of radiation on the electronic boards used for the GEM upgrade project and the impact that it has on the design of the firmware for CMS.Additionally, the work of the author on a new architecture for DAQ systems is described. The latter uses modified network topologies and novel web technologies to increase the available bandwidth on the network and yield an event-driven system. / Cette thèse de doctorat s'inscrit dans le projet de mise à niveau du spectromètre à muons du Compact Muon Solénoid (CMS) auprès du Large Hadron Collider (LHC). Après un arrêt pour maintenance prévu en 2019-2020, le LHC reprendra son programme de recherche à une luminosité de 2 $ imes$ 10^34 cm^-2 s^-1, soit deux fois sa valeur nominale. Ceci aura pour conséquence d'accroître le taux de particules auquel seront soumis les détecteurs de CMS et d'entraver l'efficacité de détection de ces derniers. Le spectromètre à muons de CMS sera tout particulièrement touché à cause du manque de redondance dans sa partie avant. Afin de palier à ce problème, il est proposé d'installer des détecteurs Gas Electron Multipliers (GEM) dans la première station à muons. La technologie GEM répond aux besoins de CMS en offrant une excellente efficacité de détection à de hauts flux de particules. Au sein de la collaboration GEM, le sous-groupe en charge du système d'acquisition de données (DAQ) doit développer l'électronique et les logiciels de gestion de la chaîne de lecture des détecteurs.Nous présentons ici le travail de l'auteur réalisé en tant que principal développeur du firmware pour l'électronique du système DAQ. Ces développements visent à créer une architecture qui achemine les données depuis l'électronique de lecture du détecteur jusqu'aux systèmes situés dans la zone de comptage, tout en offrant la possibilité de contrôler et surveiller l'ensemble des composants du DAQ. Le système mis en place a été largement testé durant deux campagnes de tests en faisceaux qui ont fourni des informations concernant la stabilité du DAQ ainsi que des mesures de l'efficacité des détecteurs. Nous décrivons également l'ensemble des travaux réalisés afin de caractériser les composants électroniques avant leur installation dans CMS ainsi que les résultats des tests d'irradiation effectués sur l'électronique du détecteur. Ces derniers permettent de mieux comprendre les conséquences des radiations sur le système et de développer des méthodes de mitigation.De plus, le travail de l'auteur sur la création d'une nouvelle architecture de système DAQ est décrit. Cette dernière combine les avancées récentes en terme de technologies web à une topologie de réseaux non-classique afin d'accroître la bande passante disponible et de créer un système réactif. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

The Large Hadron Collider (LHC) located at the European Organization for Nuclear Research (CERN) is the most powerful particle accelerator in the world in terms of collision energy and luminosity. This thesis presents a search for supersymmetric particles in proton-proton collision data recorded by the ATLAS experiment. A search for direct production of chargino and slepton pairs in a final state characterised by the presence of two leptons and missing transverse momentum is presented. This analysis is done using L = 20 fb-1 proton-proton collisions at √s = 8 TeV collected in 2012. No significant excess over background is observed. Exclusion limits at 95% confidence level on chargino, neutralino and slepton production are set. In 2011-12 the LHC was providing collisions every 50 ns. This puts very strong requirements on the energy measurement in presence of energy deposits from different collisions in the same read-out window and in the same calorimeter channel (pile-up). A quality factor computed offline for each collision and for each channel in the ATLAS Tile Calorimeter (TileCal) is studied. It is shown that the quality factor can be used to select channels that need a special treatment to account for large energy deposition from pile-up. Efficient criteria to detect pile-up in TileCal channels are proposed.

A measurement of the electron charge asymmetry in p+→W production in association with jets at sqrt{s}=7 TeV is presented. The dataset corresponds to an integrated luminosity of L=5fb^-1 recorded by the CMS detector in proton-proton collisions at the LHC. The sample represents a large increase in statistical precision with respect to previous CMS results and describes a first study of charge asymmetry measured in p+p→W+1 jet events. Full comparisons to previous results and theoretical predictions are provided and recommendations for extending the analysis to produce valuable input for future PDF models are made.

Despite making up over 80% of the matter in the universe, very little is known about dark matter. Its only well-established property is that it interacts gravitationally, but does not interact with ordinary matter through any of the other known forces. Specific details such as the number of dark matter particles, their quantum properties, and their interactions remain elusive and are only loosely constrained by experiments. In this dissertation I describe a novel search for a particular type of dark matter that couples preferentially to heavy quarks, using LHC proton-proton collisions at ATLAS. With a model-independent framework, comparisons are made to results obtained from other dark matter searches, and new limits are set on various interaction strengths.

Der Einfluss von Nichtlinearitäten höherer Ordnung der Magnetfelder auf die Leistung des Large Hadron Collider (LHC) und dessen geplante High-Luminosity-Aufrüstung, dem HL-LHC, wurde umfangreich untersucht. Insbesondere hat sich gezeigt, dass das Vorhandensein solcher Fehler in den Insertion Regions (IR) erhebliche Auswirkungen hat, bedingt durch hohe Beta-Funktionen und Feed-Down auf niedrigere Ordnungen aufgrund der Kreuzungsschemata. Augenmerk dieser Arbeit ist auf die Erforschung diverser Methoden zur effektiven Behandlung dieser Nichtlinearitäten höherer Ordnung gerichtet, mit dem Ziel, sie zu identifizieren und korrigieren, um die Strahloptik zu optimieren und die Maschinenleistung zu verbessern. Simulationsstudien werden eingesetzt, in denen mit verschiedenen Fehlerquellen assoziierte Resonanzantreibende Terme (RDTs) gezielt angegangen werden. Besondere Aufmerksamkeit gilt Dekapol- und Dodekapolfehlern, die in früheren Messungen im LHC schädliche Auswirkungen durch Feed-Down auf Amplituden-Detuning gezeigt haben. Die erwartete Erhöhung der Sensitivität der Optik gegenüber Fehlern in den IRs des HL-LHC unterstreicht weiter die Bedeutung der Behandlung dieser Fehler. Des Weitern werden Korrekturoptionen mit Hilfe der nichtlinearen Korrektorpaketen entwickelt. Experimentelle Studien werden durchgeführt, um die Ergebnisse zu validieren. Erhebliche Anstrengungen wurden unternommen, um die Feed-Down Effekte von Dekapol- und Dodekapol-Feldfehlern zu mindern. Um diese Herausforderung anzugehen, wurden neuartige Korrekturalgorithmen eingeführt, die erstmals die Dodekapol-Korrektoren in den IRs im operationellen Betrieb ansteuern. Die Ergebnisse dieser Experimente liefern wertvolle Erkenntnisse zur Minderung von Fehlern höherer Ordnung und tragen zum besseren Verständnis der Strahldynamik in modernen und zukünftigen Teilchenbeschleunigern bei. / The impact of high-order nonlinear magnetic field errors on the performance of the Large Hadron Collider (LHC) and its planned High-Luminosity upgrade, the HL-LHC, has been extensively studied. Particularly, the presence of such errors in the Insertion Regions (IR) has shown significant repercussions due to the high beta-functions and feed-down to lower orders caused by crossing schemes. This thesis aims to explore different methods for effectively addressing these high-order errors, with the ultimate goal of identifying and correcting them to optimize beam optics and enhance machine performance. Simulation studies are employed, using a novel and flexible correction algorithm developed during the course of this PhD research. Various strategies are investigated to improve corrections by targeting Resonance Driving Terms (RDTs) associated with diverse error sources. Special attention is devoted to decapole and dodecapole errors, which have demonstrated detrimental effects on amplitude detuning due to feed-down based on previous measurements in the LHC. The anticipated increase in optics sensitivity to errors in the IRs of the HL-LHC further underscores the importance of addressing these errors. Correction options are evaluated, focusing on the utilization of the nonlinear corrector packages to address errors in the new separation and recombination dipoles in the HL-LHC, where increased decapole errors had been expected. Experimental studies are conducted to validate the findings. Significant efforts are dedicated to mitigating the feed-down effects arising from decapole and dodecapole field errors. To address this challenge, novel corrections involving the operational implementation of dodecapole correctors in the IRs have been introduced for the first time. The results of these experiments provide valuable insights into the mitigation of high-order errors and contribute to the overall understanding of beam dynamics in advanced particle accelerators.

The Standard Model has been very successful over the last few decades in its agreement with experimental evidence; however there are some remaining puzzles in our understanding of the Universe which have yet to be solved. Even if the Higgs boson and Super Symmetry are discovered, questions still arise, such as why Nature is primarily made of matter when antimatter should have been produced in equal amounts at the beginning of the Universe, why the fundamental particles have the mass hierarchy that they do, what the nature of dark matter is, or whether or not quarks and leptons are themselves made of constituent parts, just to name a few. Theories Beyond the Standard Model attempt to tackle these questions, and also provide alternative explanations for electroweak symmetry breaking in case the Higgs mechanism in the Standard Model contradicts what is observed. The ATLAS detector was built to discover new physics from high-energy proton-proton collisions delivered by the Large Hadron Collider and to probe the electroweak scale with hard interactions at energies near ~1 TeV. While searching for new physics processes occurring at a much higher invariant mass than available at previous colliders, understanding the performance of the detector is crucial, especially during the first few months of running. This thesis presents a motivation for using dimuons to search for new physics in early ATLAS data, a measurement of the Z0/γ ->μμ cross section as a first test of Standard Model theoretical predictions at √s =7 TeVqqμμ, and finally a search for new physics via a four-fermion contact interaction in the dimuon channel (qqμμ) using the full 2010 data set.

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Am Large Hadron Collider und am ATLAS-Detektor werden umfangreiche Aufrüstungsarbeiten vorgenommen. Diese Arbeiten sind in mehrere Phasen gegliedert und umfassen unter Anderem Änderungen an der Ausleseelektronik der Flüssigargonkalorimeter; insbesondere ist es geplant, während der letzten Phase ihren Primärpfad vollständig auszutauschen. Die Elektronik besteht aus einem analogen und einem digitalen Teil: während ersterer die Signalpulse verstärkt und sie zur leichteren Abtastung verformt, führt letzterer einen Algorithmus zur Energierekonstruktion aus. Beide Teile müssen während der Aufrüstung verbessert werden, damit der Detektor interessante Kollisionsereignisse präzise rekonstruieren und uninteressante effizient verwerfen kann. In dieser Dissertation werden Simulationsstudien präsentiert, die sowohl die analoge als auch die digitale Auslese der Flüssigargonkalorimeter optimieren. Die Korrektheit der Simulation wird mithilfe von Kalibrationsdaten geprüft, die im sog. Run 2 des ATLAS-Detektors aufgenommen worden sind. Der Einfluss verschiedener Parameter der Signalverformung auf die Energieauflösung wird analysiert und die Nützlichkeit einer erhöhten Abtastrate von 80 MHz untersucht. Des Weiteren gibt diese Arbeit eine Übersicht über lineare und nichtlineare Energierekonstruktionsalgorithmen. Schließlich wird eine Auswahl von ihnen hinsichtlich ihrer Leistungsfähigkeit miteinander verglichen. Es wird gezeigt, dass ein Erhöhen der Ordnung des Optimalfilters, der gegenwärtig verwendete Algorithmus, die Energieauflösung um 2 bis 3 % verbessern kann, und zwar in allen Regionen des Detektors. Der Wiener Filter mit Vorwärtskorrektur, ein nichtlinearer Algorithmus, verbessert sie um bis zu 10 % in einigen Regionen, verschlechtert sie aber in anderen. Ein Zusammenhang dieses Verhaltens mit der Wahrscheinlichkeit fälschlich detektierter Kalorimetertreffer wird aufgezeigt und mögliche Lösungen werden diskutiert.:1 Introduction 2 An Overview of High-Energy Particle Physics 2.1 The Standard Model of Particle Physics 2.2 Verification of the Standard Model 2.3 Beyond the Standard Model 3 LHC, ATLAS, and the Liquid-Argon Calorimeters 3.1 The Large Hadron Collider 3.2 The ATLAS Detector 3.3 The ATLAS Liquid-Argon Calorimeters 4 Upgrades to the ATLAS Liquid-Argon Calorimeters 4.1 Physics Goals 4.2 Phase-I Upgrade 4.3 Phase-II Upgrade 5 Noise Suppression With Digital Filters 5.1 Terminology 5.2 Digital Filters 5.3 Wiener Filter 5.4 Matched Wiener Filter 5.5 Matched Wiener Filter Without Bias 5.6 Timing Reconstruction, Optimal Filtering, and Selection Criteria 5.7 Forward Correction 5.8 Sparse Signal Restoration 5.9 Artificial Neural Networks 6 Simulation of the ATLAS Liquid-Argon Calorimeter Readout Electronics 6.1 AREUS 6.2 Hit Generation and Sampling 6.3 Pulse Shapes 6.4 Thermal Noise 6.5 Quantization 6.6 Digital Filters 6.7 Statistical Analysis 7 Results of the Readout Electronics Simulation Studies 7.1 Statistical Treatment 7.2 Simulation Verification Using Run-2 Data 7.3 Dependence of the Noise on the Shaping Time 7.4 The Analog Readout Electronics and the ADC 7.5 The Optimal Filter (OF) 7.6 The Wiener Filter 7.7 The Wiener Filter with Forward Correction (WFFC) 7.8 Final Comparison and Conclusions 8 Conclusions and Outlook Appendices / The Large Hadron Collider and the ATLAS detector are undergoing a comprehensive upgrade split into multiple phases. This effort also affects the liquid-argon calorimeters, whose main readout electronics will be replaced completely during the final phase. The electronics consist of an analog and a digital portion: the former amplifies the signal and shapes it to facilitate sampling, the latter executes an energy reconstruction algorithm. Both must be improved during the upgrade so that the detector may accurately reconstruct interesting collision events and efficiently suppress uninteresting ones. In this thesis, simulation studies are presented that optimize both the analog and the digital readout of the liquid-argon calorimeters. The simulation is verified using calibration data that has been measured during Run 2 of the ATLAS detector. The influence of several parameters of the analog shaping stage on the energy resolution is analyzed and the utility of an increased signal sampling rate of 80 MHz is investigated. Furthermore, a number of linear and non-linear energy reconstruction algorithms is reviewed and the performance of a selection of them is compared. It is demonstrated that increasing the order of the Optimal Filter, the algorithm currently in use, improves energy resolution by 2 to 3 % in all detector regions. The Wiener filter with forward correction, a non-linear algorithm, gives an improvement of up to 10 % in some regions, but degrades the resolution in others. A link between this behavior and the probability of falsely detected calorimeter hits is shown and possible solutions are discussed.:1 Introduction 2 An Overview of High-Energy Particle Physics 2.1 The Standard Model of Particle Physics 2.2 Verification of the Standard Model 2.3 Beyond the Standard Model 3 LHC, ATLAS, and the Liquid-Argon Calorimeters 3.1 The Large Hadron Collider 3.2 The ATLAS Detector 3.3 The ATLAS Liquid-Argon Calorimeters 4 Upgrades to the ATLAS Liquid-Argon Calorimeters 4.1 Physics Goals 4.2 Phase-I Upgrade 4.3 Phase-II Upgrade 5 Noise Suppression With Digital Filters 5.1 Terminology 5.2 Digital Filters 5.3 Wiener Filter 5.4 Matched Wiener Filter 5.5 Matched Wiener Filter Without Bias 5.6 Timing Reconstruction, Optimal Filtering, and Selection Criteria 5.7 Forward Correction 5.8 Sparse Signal Restoration 5.9 Artificial Neural Networks 6 Simulation of the ATLAS Liquid-Argon Calorimeter Readout Electronics 6.1 AREUS 6.2 Hit Generation and Sampling 6.3 Pulse Shapes 6.4 Thermal Noise 6.5 Quantization 6.6 Digital Filters 6.7 Statistical Analysis 7 Results of the Readout Electronics Simulation Studies 7.1 Statistical Treatment 7.2 Simulation Verification Using Run-2 Data 7.3 Dependence of the Noise on the Shaping Time 7.4 The Analog Readout Electronics and the ADC 7.5 The Optimal Filter (OF) 7.6 The Wiener Filter 7.7 The Wiener Filter with Forward Correction (WFFC) 7.8 Final Comparison and Conclusions 8 Conclusions and Outlook Appendices