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Dissertations / Theses on the topic 'Compact Muon Solenoid Detector'
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1
Hansen, Maria Forbord. "Multi-jet Higgs boson study at the Compact Muon Solenoid detector." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520266.
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Wilt, Brian A. "Charged multiplicity measurement for simulated pp events in the Compact Muon Solenoid (CMS) detector." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40922.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2007.Includes bibliographical references (p. 61-64).
In this thesis, I studied the effectiveness of a method for measuring the charged multiplicity of proton-proton collisions in the Compact Muon Solenoid (CMS) experiment at LHC energies ... This technique involves counting reconstructed hits in the innermost layer of the pixel tracker. By using the relationship between pseudorapidity and deposited charge of the hits, we can distinguish between signal and background. We calculate a transformation function as the division of the average Monte Carlo track distribution by the average reconstructed hit distribution. By applying this transformation to the reconstructed hit distributions on an event-by-event basis, we can collect information about minimum bias events. This method gives us access to low PT particles which cannot be reconstructed in charged multiplicity methods using tracklets. A description of the method is given, followed by preliminary results: reconstructed Neh distributions for ... distribution.
by Brian A. Wilt.
S.B.
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Werner, Vanessa Gaultney. "Angular Distribution of Prompt Photons Using the Compact Muon Solenoid Detector at √S =7 TeV." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/727.
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The study of the angular distribution of photon plus jet events in pp collisions at √S =7 TeV with the Compact Muon Solenoid (CMS) detector is presented. The photon is restricted to the central region of the detector (|η| < 1.4442) while the jet is allowed to be present in both central and forward regions of CMS |η| < 2.4). Dominant backgrounds due to jets fragmenting into neutral mesons are accounted for through the use of a template method that discriminates between signal and background. The angular distribution, |η*|, is defined as the absolute value of the difference in η between the leading photon and leading jet in an event divided by two. The angular distribution ranging from 0-1.4 was examined and compared with next-to-leading order QCD predictions and was found to be in good agreement.
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Pol, Adrian Alan. "Machine Learning Anomaly Detection Applications to Compact Muon Solenoid Data Quality Monitoring." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS083.
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La surveillance de la qualité des données qui proviennent des expériences de physique des hautes énergies est une tâche exigeante mais cruciale pour assurer que les analyses physiques sont basées en données de la meilleure qualité possible. Lors de l’expérience Compact Muon Solenoid opérant au Grand collisionneur de hadrons du CERN, le paradigme actuel d’évaluation de la qualité des données est basé sur l’examen détaillé d’un grand nombre de tests statistiques. Cependant, la complexité toujours croissante des détecteurs et le volume des données de surveillance appellent un changement de paradigme. Ici, les techniques de Machine Learning promettent une percée. Cette thèse traite du problème de l’automatisation applique à la surveillance de la qualité des données avec les méthodes de détection des anomalies d’apprentissage automatique. La grande dimensionnalité des données empêche l’utilisation de méthodes de détection classiques, pointant vers de nouvelles, basées sur l’apprentissage en profondeur. Les anomalies causées par un dysfonctionnement du détecteur sont difficiles à énumérer a priori et rares, ce qui limite la quantité de données étiquetées. Ainsi, cette thèse explore le paysage des algorithmes existants avec une attention particulière aux problèmes semi-supervisés et démontre leur validité et leur utilité sur des cas de test réels en utilisant les données de l’expérience. Dans le cadre de ce projet, l’infrastructure de surveillance a été encore optimisée et étendue, offrant des méthodes plus sensibles aux différents modes de défaillanceThe Data Quality Monitoring of High Energy Physics experiments is a crucial and demanding task to deliver high-quality data used for physics analysis. At the Compact Muon Solenoid experiment operating at the CERN Large Hadron Collider, the current quality assessment paradigm, is based on the scrutiny of a large number of statistical tests. However, the ever increasing detector complexity and the volume of monitoring data call for a growing paradigm shift. Here, Machine Learning techniques promise a breakthrough. This dissertation deals with the problem of automating Data Quality Monitoring scrutiny with Machine Learning Anomaly Detection methods. The high-dimensionality of the data precludes the usage of classic detection methods, pointing to novel ones, based on deep learning. Anomalies caused by detector malfunctioning are difficult to enumerate a priori and rare, limiting the amount of labeled data. This thesis explores the landscape of existing algorithms with particular attention to semi-supervised problems and demonstrates their validity and usefulness on real test cases using the experiment data. As part of this project, the monitoring infrastructure was further optimized and extended, delivering methods with higher sensitivity to various failure modes
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Wardrope, David Robert. "Preparations for measurement of electroweak vector boson production cross-sections using the electron decay modes, with the Compact Muon Solenoid detector." Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/5517.
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The Compact Muon Solenoid was designed to make discoveries at the TeV scale : to elucidate the nature of electroweak symmetry breaking and to search for physics beyond the Standard Model. For any such discovery to be credible, it must first be demonstrated that the CMS detector is understood. One mechanism to make this demonstration is to measure "standard candle" processes, such as W and Z production. This thesis describes preparations undertaken to make these measurements using the electron decay modes, with [derivative]Ldt = 10 pb-1 of collision data. The energy resolution of the electromagnetic calorimeter was measured in test beam data. An improved method of deriving the optimised weights necessary for amplitude reconstruction is described. The measurement of electron charge using tracks is impaired by the electron showering in the tracker material. A novel charge measurement technique that is complementary to the existing method was assessed. Missing transverse energy is a powerful discriminating variable for the selection of W+/ -> e+/ [upsilon]e events, however it is difficult to simulate accurately due to its global nature. The Ersatz Missing Energy method was developed to provide reliable and accurate descriptions of missing energy from data using readily reconstructible [gamma]*/Z -> e+e- events. The method is described and evaluated. Finally, the measurement strategy for W and Z boson production cross-sections in early data is outlined and analysed using simulated data. Significant results can be obtained with only [derivative] Ldt = 10 pb-1.
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Deelen, Nikkie [Verfasser], and W. de [Akademischer Betreuer] Boer. "Characterizing detector modules for the Upgrade of the Silicon Tracker of the Compact Muon Solenoid experiment / Nikkie Deelen ; Betreuer: W. de Boer." Karlsruhe : KIT-Bibliothek, 2019. http://d-nb.info/120141492X/34.
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Sciacca, Francesco G. P. "Analogue readout and signal processing for micro strip gas chambers of the compact muon solenoid at LHC." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391719.
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Bell, Alan James. "The design and construction of the beam scintillation counter for CMS." Thesis, University of Canterbury. Physics and Astronomy, 2008. http://hdl.handle.net/10092/1588.
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This thesis presents the design qualification and construction of the Beam Scintillator Counter (BSC) for the CMS Collaboration at CERN in 2007 - 2008. The BSC detector is designed to aid in the commissioning of the Compact Muon Solenoid (CMS) during the first 2 years of operation and provide technical triggering for beam halo and minimum-bias events. Using plastic scintillator tiles mounted at both ends of CMS, it will detect minimum ionizing particles through the low-to-mid luminosity phases of the Large Hadron Collider (LHC) commissioning. During these early phases, the BSC will provide probably the most interesting and widely used data of any of the CMS sub-detectors and will be employed in the track based alignment procedure of the central tracker and commissioning of the Forward Hadron Calorimeter.
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Bernardes, César Augusto. "Busca por dimensões extras universais no Detector CMS do LHC : o canal com dois múons de mesma carga." reponame:Repositório Institucional da UFABC, 2012.
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Zenoni, Florian. "Study of Triple-GEM detectors for the CMS muon spectrometer upgrade at LHC and study of the forward-backward charge asymmetry for the search of extra neutral gauge bosons." Doctoral thesis, Universite Libre de Bruxelles, 2016. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/229354.
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Cette thèse de doctorat a pour cadre l’expérience CMS auprès du grand collisionneur de protons du CERN, le LHC. Le LHC, qui a permis la découverte en 2012 du boson de Brout-Englert-Higgs, est destiné à fonctionner pour encore 20 ans, avec une luminosité qui croîtra progressivement pour atteindre d’ici 2025 la valeur de 7.5 x 10^34 cm^-2 s^-1, c'est à dire environ cinq fois la valeur initialement prévue. Ceci a pour conséquence que les expériences doivent s’adapter et mettre à niveau une série de leurs composants et détecteurs. Une des prochaines mises à niveau de l’expérience CMS concerne les détecteurs Triple Gas Electron Multiplier (GEM) qui sont actuellement en développement pour la partie avant du spectromètre à muons de l’expérience. Ces détecteurs seront installés dans CMS durant le deuxième long arrêt du LHC, en 2018-2019, appelé LS2. Cette mise à niveau a pour but de contrôler les taux de déclenchement d’événements pour la détection de muons, grâce à la haute performance de ces détecteurs Triple GEM en présence de taux de particules extrêmement élevés (>1 kHz/cm^2). De plus, grâce à sa très bonne résolution spatiale (~250 um), la technologie GEM peut améliorer la reconstruction des traces de muons et la capacité d’identification du détecteur avant.Le but de mon travail de recherche est d’estimer la sensitivité des Triple GEMs à l’environnement de radiation hostile dans CMS, essentiellement composé de neutrons et de photons produits lors des interactions entre les particules et les détecteurs constituant l’expérience CMS. L’estimation précise de cette sensitivité est très importante, car une sous-estimation pourrait avoir des effets désastreux pour l’efficacité des Triple GEMs une fois installés dans CMS. Pour valider mes simulations, j’ai également reproduit des résultats expérimentaux obtenus avec d’autres détecteurs similaires déjà installés dans CMS, tels que les Resistive Plate Chambers (RPC).La deuxième partie de mon travail concerne l’étude de la capacité de l’expérience CMS à discerner différents modèles de nouvelle physique prédisant l’existence de bosons vecteurs, appelés Z'. Ces modèles font partie des extensions plausibles du Modèle Standard. En particulier, l’analyse se concentre sur des simulations dans lesquelles le Z' se désintègre en deux muons, et sur l’impact que les mises à niveau avec les détecteurs Triple GEM apporteront à ces mesures tout le long de la phase de haute intensité du LHC. Mes simulations montrent que plus de 20% des événements simulés comptent au moins un muon dans la région en pseudo-rapidité (eta) de CMS couverte par les détecteurs Triple GEM. Les résultats préliminaires démontrent que, dans le case de modèles à 3 TeV/c^2, il sera possible dès la fin de la Phase I de distinguer un Z'I d'un Z'SSM avec un niveau de signification alpha > 3 sigma.This PhD thesis takes place in the CMS experiment at CERN's Large Hadron Collider (LHC). The LHC allowed the discovery of the Brout-Englert-Higgs boson in 2012, and is designed to run for at least 20 years, with an increasing luminosity that will reach by 2025 a value of 7.5 x 10^34 cm^-2 s^-1, that is a yield five times greater than the one initially intended. As a consequence, the experiments must adapt and upgrade many of their components and particle detectors. One of the foreseen upgrades of the CMS experiment concerns the Triple Gas Electron Multiplier (GEM) detectors, currently in development for the forward muon spectrometer. These detectors will be installed in CMS during the second long LHC shutdown (LS2), in 2018-2019. The aim of this upgrade is to better control the event trigger rate at Level 1 for muon detection, thanks to the high performance of these Triple GEM detectors, in presence of very high particle rates (>1 kHz/cm^2). Moreover, thanks to its excellent spatial resolution (~250 um), the GEM technology can improve the muon track reconstruction and the identification capability of the forward detector.The goal of my research is to estimate the sensitivity of Triple GEMs to the hostile background radiation in CMS, essentially made of neutron and photons generated by the interaction between the particles and CMS detectors. The accurate evaluation of this sensitivity is very important, as an underestimation could have ruinous effects of the Triple GEMs efficiency, once they are installed in CMS. To validate my simulations, I have reproduced experimental results obtained with similar detectors already installed in CMS, such as the Resistive Plate Chambers (RPC).The second part of my work regards the study of the CMS experiment capability to discriminate between different models of new physics predicting the existence of neutral vector bosons called Z'. These models belong to plausible extensions of the Standard Model. In particular, the analysis is focused on simulated samples in which the Z' decays in two muons, and on the impact that the Triple GEM detectors upgrades will bring to these measurements during the high luminosity phase of the LHC, called Phase II. My simulations prove that more than 20% of the simulated events see at least one muon in the CMS pseudo-rapidity (eta) region covered by Triple GEM detectors. Preliminary results show that, in the case of 3 TeV/c^2 models, it will be possible already at the end of Phase I to discriminate a Z'I from a Z'SSM with a significance level alpha > 3 sigma.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Tiras, Emrah. "Characterization of 900 four-anode photomultiplier tubes for use in 2013 hadronic forward calorimeter upgrade." Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/3392.
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The first 900 four-anode Photomultiplier Tubes (PMTs) have been evaluated for use in the 2013 Hadronic Forward (HF) calorimeter upgrade. HF is a part of the Compact Muon Solenoid (CMS), which is one of the two large general-purpose particle detectors of the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland. HF requires 1728 PMTs. These small tubes are the sensitive light detectors that provide the output signals of HF. Before installing PMTs in HF, their quality control demands need to be satisfied. These tests, done at the University of Iowa, are designed in three categories to test seventeen different parameters for each PMT. The three most basic and most important groups of parameters are: dark current, gain (anode and cathode), and timing. There are secondary tests which are performed on a smaller percentage of the PMTs such as surface uniformity, double pulse and single photo-electron resolution. The PMTs that meet the specifications of HF will be sent to CERN where they are expected to be in use for at least a decade.
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López, Mateos David. "Jet quenching in the compact muon solenoid at the LHC." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32901.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (p. 85-88).
In this thesis we perform analyses on simulated data that allow us to demonstrate the sensitivity of the CMS experiment to certain jet quenching observables. In particular, two theoretical scenarios which mimic RHIC data at low PT and which show either no quenching or BDMPS-based quenching at high PT are formulated. The difference between these two scenarios is analyzed for RAA, RCP at different centralities and jet-specific observables such as jet energy spectra, fragmentation functions and jet profiles. We show how these analyses indicate that the large acceptance of the CMS detector, combined with the high granularity in the energy resolution of the calorimeter will be essential tools in studying the phenomenon of jet quenching. Finally, we propose extensions to this work in preparation to analyzing the data from Pb-Pb runs at the LHC. Disclaimer: The work on this thesis does not model the CMS detector geometry with the accuracy required for official analyses, which are fully representative of the CMS detector capabilities. Such analyses require of the full CMS simulation machinery and are left to the CMS Heavy Ion group as a whole.
by David López Mateos.
S.B.
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Goitom, Israel. "Track quality monitoring for the compact muon solenoid silicon strip tracker." Thesis, Brunel University, 2009. http://bura.brunel.ac.uk/handle/2438/3785.
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The CMS Tracker is an all silicon detector and it is the biggest of its kind to be built. The system consists of over 15,000 individual detector modules giving rise to readout through almost 107 channels. The data generated by the Tracker system is close to 650 MB at 40 MHz. This has created a challenge for the CMS collaborators in terms of data storage for analysis. To store only the interesting physics data the readout rate has to be reduced to 100 Hz where the data has to be ltered through a monitoring system for quality checks. The Tracker being the closest part of the detector to the interaction point of the CMS creates yet another challenge that needs the data quality monitoring system. As it operates in a very hostile environment the silicon detectors used to detect the particles will be degraded. It is very important to monitor the changes in the sensor behaviour with time so that to calibrate the sensors to compensate for the erroneous readings. This thesis discusses the development of a monitoring system that will enable the checking of data generated by the tracker to address the issues discussed above. The system has two parts, one dealing with the data used to monitor the Tracker and a second one that deals with statistical methods used to check the quality of the data.
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Clergeau, Jean-François. "Etude d'un détecteur gazeux à micropistes pour l'expérience Compact Muon Solenoid." Lyon 1, 1997. http://www.theses.fr/1997LYO10139.
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Les detecteurs gazeux a micropistes msgc (micro-strip gas chamber) ont ete proposes pour la premiere fois par a. Oed en 1988. Ces detecteurs, issus des chambres a fils inventees par g. Charpak, ont pu etre realises grace aux avancees technologiques dans le domaine de la micro-electronique. Les fils des compteurs gazeux traditionnels ont ete remplaces par des pistes metalliques gravees a l'echelle du micron sur un substrat isolant. La granularite obtenue dans les compteurs msgc leur permet de fonctionner sous un flux eleve de particules, grace a une collection rapide de la charge. Elle contribue aussi a la mesure des impacts avec de bonnes resolutions spatiale et temporelle. Les msgc sont donc bien adaptes pour etre utilises dans les conditions experimentales attendues aupres du futur collisionneur lhc (large hadron collider) au cern. Ce travail, realise a l'institut de physique nucleaire de lyon au sein de la collaboration cms (compact muon solenoid), l'une des quatre experiences proposees au lhc, montre qu'il est possible d'utiliser les msgc dans le champ magnetique de 4 tesla prevu pour cms a condition de compenser l'influence de celui-ci par inclinaison des detecteurs. Il est aussi montre que la mesure des impacts dans un tres haut flux de particules ( 10#4 hz/mm#2), en particulier la separation des croisements de faisceaux, intervenant toutes les 25 ns au lhc, necessite une adaptation de l'electronique de lecture et du traitement du signal delivre par ce type de detecteur.
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Munro, Craig. "Distributed data analysis using the Grid for the compact muon solenoid experiment." Thesis, Brunel University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443535.
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Bein, Samuel Louis. "Targeting the minimal supersymmetric standard model with the compact muon solenoid experiment." Thesis, The Florida State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10161255.
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An interpretation of CMS searches for evidence of supersymmetry in the context of the minimal supersymmetric Standard Model (MSSM) is given. It is found that supersymmetric particles with color charge are excluded in the mass range below about 400 GeV, but neutral and weakly-charged sparticles remain non-excluded in all mass ranges. Discussion of the non-excluded regions of the model parameter space is given, including details on the strengths and weaknesses of existing searches, and recommendations for future analysis strategies. Advancements in the modeling of events arising from quantum chromodynamics and electroweak boson production, which are major backgrounds in searches for new physics at the LHC, are also presented. These methods have been implemented as components of CMS searches for supersymmetry in proton-proton collisions resulting in purely hadronic events (i.e., events with no identified leptons) at a center of momentum energy of 13 TeV. These searches, interpreted in the context of simplified models, exclude supersymmetric gluons (gluinos) up to masses of 1400 to 1600 GeV, depending on the model considered, and exclude scalar top quarks with masses up to about 800 GeV, assuming a massless lightest supersymmetric particle. A search for non-excluded supersymmetry models is also presented, which uses multivariate discriminants to isolate potential signal candidate events. The search achieves sensitivity to new physics models in background-dominated kinematic regions not typically considered by analyses, and rules out supersymmetry models that survived 7 and 8 TeV searches performed by CMS.
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Noy, Matthew. "Development and characterisation of the compact muon solenoid strip tracker front end driver." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416357.
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Kaganas, Gary H. "Comparing Remote Data Transfer Rates of Compact Muon Solenoid Jobs with Xrootd and Lustre." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1534.
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To explore the feasibility of processing Compact Muon Solenoid (CMS) analysis jobs across the wide area network, the FIU CMS Tier-3 center and the Florida CMS Tier-2 center designed a remote data access strategy. A Kerberized Lustre test bed was installed at the Tier-2 with the design to provide storage resources to private-facing worker nodes at the Tier-3. However, the Kerberos security layer is not capable of authenticating resources behind a private network. As a remedy, an xrootd server on a public-facing node at the Tier-3 was installed to export the file system to the private-facing worker nodes. We report the performance of CMS analysis jobs processed by the Tier-3 worker nodes accessing data from a Kerberized Lustre file. The processing performance of this configuration is benchmarked against a direct connection to the Lustre file system, and separately, where the xrootd server is near the Lustre file system.
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Whyntie, Tom. "Constraining the supersymmetric parameter space with early data from the Compact Muon Solenoid experiment." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9626.
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The year 2010 saw the Large Hadron Collider (LHC) collect 35:1 pb-1 of 7TeV proton-proton collision data. This thesis reports on the work carried out by the candidate as part of the calculation of the first constraints placed upon the supersymmetric parameter space using measurements made with this data. In particular, the development and application of the kinematic techniques used to ensure that the search was robust to detector mismeasurements, inherent in any early phase of data-taking, are discussed. The Constrained Minimally Supersymmetric Standard Model (CMSSM) is introduced to demonstrate how supersymmetry may extend the Standard Model of particle physics, and is used as the benchmark signal to investigate how supersymmetry may appear in 7TeV proton-proton collisions. The role of kinematics in early searches for such signals is then discussed; given the final state topology of interest (particle jets and large missing transverse momentum), particular attention is paid to errors that are due to detector mismeasurements, and how these may be accounted for with an appropriate choice of observable. A search strategy based upon these principles and applied to the Compact Muon Solenoid (CMS) experiment is then described, as used in the first published search for supersymmetry with LHC data reported in Phys. Lett. B 698 (2011) 196. The kinematic characterisation of events discussed above is exploited to ensure that the search is robust to mismeasurement. The thesis concludes with a summary of the search results. The observed number of events fulfilling the signal criteria is compatible with that expected from the Standard Model alone. The subsequent exclusion limits, given at the 95% Confidence Level, place significantly greater constraints upon the supersymmetric parameter space than those of previous experiments.
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Huckvale, Benedict James. "Studying anomalous WWγ couplings and developing the global calorimeter trigger control system for the CMS experiment." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505753.
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The rate of decay of the process W -> Wγ is well-defined by the Standard Model, so measured deviation is a strong but indirect indicator of non-Standard Model physics. Deviations of this coupling strength can be parameterized, in a model independent, general sense, into two parameters, Δk and λ.
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Karavakis, Edward. "A distributed analysis and monitoring framework for the compact Muon solenoid experiment and a pedestrian simulation." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4409.
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The design of a parallel and distributed computing system is a very complicated task. It requires a detailed understanding of the design issues and of the theoretical and practical aspects of their solutions. Firstly, this thesis discusses in detail the major concepts and components required to make parallel and distributed computing a reality. A multithreaded and distributed framework capable of analysing the simulation data produced by a pedestrian simulation software was developed. Secondly, this thesis discusses the origins and fundamentals of Grid computing and the motivations for its use in High Energy Physics. Access to the data produced by the Large Hadron Collider (LHC) has to be provided for more than five thousand scientists all over the world. Users who run analysis jobs on the Grid do not necessarily have expertise in Grid computing. Simple, userfriendly and reliable monitoring of the analysis jobs is one of the key components of the operations of the distributed analysis; reliable monitoring is one of the crucial components of the Worldwide LHC Computing Grid for providing the functionality and performance that is required by the LHC experiments. The CMS Dashboard Task Monitoring and the CMS Dashboard Job Summary monitoring applications were developed to serve the needs of the CMS community.
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Petridis, Torres Konstantinos A. "Reconstruction and selection of Z→ττ→e+τ-jet decays at the compact muon solenoid experiment." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508935.
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St, John Jason Michael. "A search for new resonances with the dijet angular ratio using the Compact Muon Solenoid Experiment." Thesis, Boston University, 2012. https://hdl.handle.net/2144/31606.
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Thesis (Ph.D.)--Boston UniversityPLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
A search for dijet resonances is performed using 2.2 fb-1 of proton-proton collision data at [Special characters omitted.] = 7 TeV recorded by the CMS detector at CERN. The study is based on the dijet angular ratio, the ratio of the number of events with the two leading jets having pseudorapidity difference |Δη| < 1.3 to the number of events with 1.3 < |Δη| < 3.0. Models of new resonances which decay into two jets typically predict dijet angular distributions and hence, values of the dijet angular ratio which differ from standard model processes. We thus use the measurement of the angular ratio as a function of mass to set limits on the cross sections of new spin-1⁄2 quark-gluon resonances. We exclude excited quarks of mass less than 3.2 TeV at 95% confidence level, where a limit of 2.8 TeV is expected.
2031-01-01
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Pozzobon, Nicola. "A Level 1 Tracking Trigger for the CMS Experiment at the LHC Phase 2 Luminosity Upgrade." Doctoral thesis, Università degli studi di Padova, 2011. http://hdl.handle.net/11577/3422049.
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The second decade of Large Hadron Collider operations, from about 2020 onwards, envisages a remarkable increase in collider instantaneous luminosity, one order of magnitude above the project one. This luminosity increase presents several challenges to the LHC experiments. The present Tracker of the Compact Muon Solenoid experiment must be replaced with a system providing excellent tracking quality at higher luminosities, as well as Tracking Trigger inputs to the existing "Level 0" CMS Trigger system at the full 40 MHz bunch-crossing rate. The minimal requirements for a Tracking Trigger would be the capability to confirm the presence of high-pT tracks associated with Calorimeter and/or Muon Level 0 Triggers. The ability to provide effective isolation criteria may also be required, and would in any case substantially improve the Trigger performance.
Maintaining the data rates generated by Tracking Trigger inputs within a manageable bandwidth requires sensor modules able to locally sparsify the data. Measuring at detector module level the track direction in the transverse plane, and hence deriving its transverse momentum, is the most promising solution to provide such a detector-embedded data reduction feature. These so-called "pT-modules"' would only transmit to the Level 1 Trigger "stubs", pairs of correlated hits in two closely separated sensors, derived by tracks with pT above a given threshold. To exemplify, a 2 GeV/c threshold would cut data rate of more than a factor 10, hence providing a data rate well within the capabilities of present data links.
The pT-modules design discussed in this work consists of two, closely spaced segmented silicon sensors, featuring both pattern hit correlation across the module and a single hit position resolution high enough to compute stubs with the required accuracy to resolve track directions despite a lever arm of about only 1 mm. A concept Tracker layout, the so-called "Long Barrel", consisting in an Outer Tracker completely built out of pT-modules, has been proposed. The Long Barrel Tracker is particularly flexible in simulation studies of Tracking Trigger as it allows for information from several layers of the Tracker to be combined in a projective geometry. For this reason, it is meant as a testing ground to compare the performance of different designs and configurations. The Long Barrel layout also allows the generation of even more structured Trigger Objects such as "tracklets", consisting of pairs of stubs in opportunely paired layers, which can in turn be used as seeds to generate "Level 1 tracks", including even more stubs.
The choice of stacked sensors for pT-modules has been recently strengthened by test beam results obtained with novel prototypes of Monolithic Active Pixel Sensors and reported in this thesis. The developement of Tracking Trigger simulations is also presented as a major step towards the design of a realistic Trigger capable Tracker upgrade. A particular challenge for the Trigger system is given by tau leptons produced in many rare processes searched at the LHC. The performance of a Tracking Trigger on final states with tau leptons will be crucial at very high luminosities and is presented at the and of this document as the natural step forward in the work on the subject.Durante il secondo decennio di operazioni al Large Hadron Collider, a partire dall'anno 2020, è previsto un notevole aumento della luminosità istantanea del collisionatore, di un ordine di grandezza superiore rispetto a quella di progetto. Questa luminosità presenta numeose sfide per gli esperimenti a LHC. Il Tracciatore attualmente impiegato nell'esperimento Compact Muon Solenoid dovrà essere rimpiazzato con un sistema in grado di garantire una tracciatura di qualità eccellente ad alte luminosità e, allo stesso tempo, fornire informazioni utili per l'attuale "Livello 0" del sistema di Trigger a CMS, alla frequenza di collisioni di 40 MHz. Le richieste minime per un Trigger basato sul Tracciatore sono la capacità di confermare la presenza di tracce ad alto pT associate a Trigger di Livello 0 ottenuti con i Calorimetri o i rivelatori di muoni. La capacità di fornire criteri efficaci di isolazione può essere ulteriormente richiesa e in ogni caso migliorerebbe significativamente le prestazioni del Trigger. Il rateo dei dati associati con la generazione nel Tracciatore di informazione di Trigger può essere mantenuto in una larghezza di banda sufficientemente maneggevole richiedendo che i moduli sensitivi siano in grado di ridurre localmente i dati. I principali candidati per una simile riduzione locale del rateo i dati sono caratterizzati dalla capacità di fornire la direzione della traccia nel piano trasverso, oltre alla sua posizione, da cui poter dedurre la quantità di moto della traccia stessa. Questi "pT-modules" trasmetterebbero di conseguenza al Trigger di primo livello degli abbozzi di traccia ("stub") generati da particelle con pT al di sopra di 2 GeV/c. La scelta di una simile soglia permetterebbe la riduzione dei dati di un fattore superiore a 10, consentendo quindi un rateo facilmente tollerabile. I moduli di Trigger possono essere realizzati con due sensori di silicio paralleli leggermente separati, caratterizzati da una risoluzione sulla misura del singolo punto d'impatto tale che gli stub, ottenuti tramite correlazione tra i punti misurati nel modulo, possano fornire un'adeguata misura della direzione della traccia, nonostante il braccio di leva sia dell'ordine del millimetro. Un'ipotetica configurazione per il Tracciatore, composto da "lunghi barili", che prevede un Tracciatore esterno realizzato totalmente con moduli di Trigger, è stata proposta. Essa è particolarmente flessibile negli studi di simulazione per il Trigger realizzato con il Tracciatore giacché consente di combinare tra loro, tramite proiezioni geometriche, le informazioni provenienti da diversi strati del Tracciatore. Pertanto è un campo di prova per confrontare le prestazioni di diverse concezioni e diverse configurazioni. Il Tracciatore proposto permette anche la generazione di oggetti più articolati degli stub per il Trigger, come ad esempio le "tracklet", che consistono in coppie di stub opportunamente associate tra loro, le quali possono a loro volta essere usate come punto di partenza per la costruzione di Tracce di Primo Livello. La scelta di moduli di Trigger realizzati con sensori accoppiati è rafforzata da risultati recenti ottenuti con dei prototipi innovativi di rivelatori a Pixel Monolitici durante dei test sotto fascio riportati in questa tesi. Lo sviluppo di simulazioni per un Trigger con il Tracciatore è anch'esso presentato come un significativo progresso verso la progettazione di un nuovo Tracciatore realistico e capace di fornire informazioni utili per il Trigger. Particolarmente impegnativo è lo sforzo per un Trigger che selezioni i leptoni tau prodotti in numerosi processi rari di interesse per gli esperimenti a LHC. Le prestazioni di un Trigger con il Tracciatore su stati finali contenenti leptoni tau saranno fondamentali a luminosità molto elevate e sono illustrate alla fine di questo documento, come naturale prosecuzione del lavoro descritto.
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Price, Timothy James. "Development of dense scintillating hard fluoride glasses for the electromagnetic caorimeter of the proposed compact muon solenoid." Thesis, Brunel University, 1994. http://bura.brunel.ac.uk/handle/2438/5406.
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Hafnium based Heavy Metal Fluoride glasses have been produced and evaluated in a search for new dense scintillating materials. The principal motivation was the electromagnetic calorimeter of the Compact Muon Solenoid (CMS), a proposed detector for the Large Hadron Collider (LHC) at CERN, Geneva. Incorporating CeF 3 in these transparent glasses results in scintillators with fast time constants that are typical of crystalline CeF 3. Typical decay components of 9 ns (30 %) and 25 ns (70 %) have been measured. To record the time distribution of scintillation light, an extension to the single-photon method, has been developed, it is optimised for materials with low light output. An alternative acquisition system which used a Multi-Channel Scaler has been critically evaluated for this application. A low dose rate (1.2 rads- I) 60CO irradiation has been used to determine the radiation tolerance of the glasses. Radiation induced optical absorbance was predominantly located in the UV with tails extending into the visible region. These glasses show partial recovery of optical absorbance at room temperature. Compositional optimisation has shown that Indium and Cerium enhance radiation tolerance.
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McLeod, Elaine Mary. "An investigation of lead tungstate crystals for use in the compact muon solenoid at the large hadron collider." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413758.
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Hays, Jonathan Michael. "Performance of a lead tungstate crystal electromagnetic calorimeter for the compact muon solenoid experiment at the large hadron collider." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325489.
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Pi, Haifeng. "Reconstruction of missing transverse energy and prospect of searching for Higgs boson produced via vector boson fusion in compact muon solenoid experiment." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013000.
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Ji, Weifeng. "Search for the decays of stopped exotic long-lived particles produced in P-P collisions at 13 TeV at CMS." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524216345344165.
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Brinson, Jessica. "A search for disappearing tracks in proton-proton collisions at sqrt(s) = 8 TeV." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1428940893.
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Scurlock, Bobby Joe. "Compact muon solenoid discovery potential for the minimal supergravity model of supersymmetry in single muon events with jets and large missing transverse energy in proton-proton collisions at center-of-mass energy 14 TEV." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0015695.
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Tschudi, Yohann. "Reconstruction de muons cosmiques en collision et recherche de gluinos se désintégrant en stop-top dans l’expérience CMS au LHC." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10152/document.
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L'expérience CMS (Compact Muon Solenoid), construite sur l'anneau du LHC (Large Hadron Collider), enregistre des données provenant des collisions proton-proton depuis 2 ans. L'alignement entre toutes les couches du trajectographe, sous-détecteur de CMS permettant la reconstruction et la mesure de l'impulstion des particules chargées, est effectué à l'aide de traces de particules créées lors de la collision et des traces créées par le passage de muons d'origine cosmique à travers ce détecteur. La première partie de ce livre sera dédiée à la reconstruction des traces de ces muons lors des collisions. Une nouvelle méthode, appelée reconstruction cosmique régionale, a été développée et mise en place. L'efficacité de 69% et le taux de faux de l'ordre de 1% permettent l'utilisation de ces traces pour l'alignement. La deuxième partie, portant sur l'analyse des données de collision, s'intéressera à la recherche de particules prédites par un modèle d'extension du Modèle Standard, la Supersymétrie, dans un scénario particulier, le scénario du Stop Léger. Dans le cas d'un fort mélange dans la troisième génération de squarks, le stop, partenaire supersymétrique du quark top, peut être léger. Dans l'analyse effectuée au cours de cette thèse, nous nous sommes intéressés au cas au mstop < mtop. Dans le MSSM avec conservation de la R-parité, le gluino serait formé par paire et se désintégrerait en un squark stop et un quark top. Le stop se désintégrerait quant-à-lui en un quark c et un neutralino, particule supersymétrique la plus légère du modèle, stable et interagissant faiblement. Aucun excès par rapport aux prédictions du Modèle Standard n'a été relevé en utilisant les 40pb-1 de données enregistrées par CMS en 2010. Les limites obtenues à 95% de niveau de confiance permettent d'exclure des masses de stop jusqu'à 175 GeV pour des masses de gluinos allant jusqu'à 350 GeV et des faibles différences de masses entre le stop et le neutralinoThe CMS experiment (Compact Muon Solenoid), built on the ring of the LHC (Large Hadron Collider), is recording data from proton-proton collisions for 2 years now. The alignment between all layers of the tracker, the sub-detector of CMS allowing the reconstruction and the measurement of the momentum of charged particles, is made by using tracks of particles created during collisions and tracks created by the passage of cosmic muons through this sub-detector. A first part of the presentation will be dedicated to the reconstruction of the tracks of these cosmic muons during collisions. A new method, called regional cosmic reconstruction, was developed and implemented. The 69 % efficiency and the fake rate around 1 % allow to use these tracks for the alignment. The second part, dedicated to the analysis of collision data, will concern the search of particles predicted by a model of extension of the Standard Model, the Supersymmetry, in a particular scenario, the light Stop scenario. In the case of a strong mixing in the third generation of squarks, the stop, supersymmetric partner of the top quark, could be light. In the analysis developped during this thesis, we were interested in the case where the mstop < mtop. In the MSSM with R-parity conservation, the gluino would be created by pair and would decay in a stop squark and a top quark. Stop would decays in a c quark and a neutralino, the lightest supereymmetric particle of the model, stable and interacting weakly. No excess with regards to Standard Model predictions was observed in 40pb-1 of data recorded by CMS in 2010. The limits obtained at 95 % confidence level allow to exclude masses of stop until 175 GeV for masses of gluinos going up to 350 GeV and low differences of masses between stop and neutralino
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Descamps, Julien. "Etude et optimisation des performances du calorimètre électromagnétique de l'expérience CMS pour la physique au LHC." Paris 6, 2007. http://www.theses.fr/2007PA066136.
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L’expérience CMS (Compact Muon Solenoid) est l’une des deux expériences généralistes du collisionneur proton-proton LHC (Large Hadron Collider) actuellement en cours de démarrage au CERN à Genève. Les premiers chapitres de cette thèse présentent le LHC, le détecteur CMS et plus particulièrement son calorimètre électromagnétique (ECAL). Est présentée ensuite une analyse des tests réalisés en 2004 avec un faisceau d’électrons de différentes énergies (20-250 GeV) dirigé vers une partie (1/36) du baril du calorimètre. Une étude de la variation de la mesure de l’énergie a été menée afin de déduire une méthode de correction. Le dernier chapitre de cette thèse présente une application de cette méthode de correction aux électrons et aux photons engendrés par une simulation complète de CMS dans laquelle la reconstruction de l’énergie est considérablement compliquée par rapport à la configuration des tests en faisceau. Un algorithme novateur de reconstruction de l’énergie des électrons et des photons a été développé pour tenir compte de cette complication et appliquer la méthode de correction étudiée en tests en faisceau.
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Killewald, Phillip. "Measuring physical properties of the W boson in 7 TeV proton-proton collisions." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1281636776.
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Zhang, Fengwangdong. "Measurement of jet production in association with a Z boson at the LHC and jet energy correction calibration at high level trigger in CMS." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/251804.
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This PhD dissertation presents the measurement of the cross section of jet production in association with a Z boson in proton-proton collisions at the Large Hadron Collider in CERN, with a center-of-mass energy of 8 TeV in 2012 and of 13 TeV in 2015. The data used for this analysis were collected by the Compact Muon Solenoid (CMS) detector, with an integrated luminosity of 19.6 fb-1 in 2012 and of 2.25 fb-1 in 2015. The differential cross section is measured as a function of jet multiplicity, jet transverse momentum and rapidity, and the scalar sum of jet transverse momenta. The rapidity correlations between the Z boson and jets are also measured benefiting from the large statistics of data taken in 2012. All distributions of measured observables are obtained after correcting detector effects using unfolding approach, and the results of two leptonic decaying channels of Z boson are combined. Coming along with the systematic and statistical uncertainties, the measurement is compared to different theoretical predictions at different accuracy levels. The predictions are from MADGRAPH 5, SHERPA 2 (for 8 TeV analysis only), MADGRAPH_AMC@NLO, and fixed next-to-next-to-leading order (for 13 TeV analysis only). Thanks to the unprecedented high energy and the large statistics of data, precision measurement is accomplished in a physical phase space never reached before. This measurement provides precise systematics for different theoretical models. It also quantifies the improvement with higher order of perturbative quantum chromodynamics calculations on matrix elements relative to the leading order multi-leg approach. In particular to the rapidity correlation study, new matching schemes (FxFx and MEPS@NLO) for next-to-leading order matrix elements and parton shower show significant improvements with respect to the MLM matching scheme for leading order multi-leg matrix elements and parton shower. This measurement also gives precise background estimation for the measurements of many other processes in Standard Model like top quark production and gauge boson couplings, and for new physics searches such as Supersymmetry. In this thesis, the jet energy correction and calibration for the high level trigger system of CMS are also depicted. From 2012 to 2015, the Large Hadron Collider was upgraded, not only with the center-of-mass energy of the beams enlarged, but also with the instantaneous luminosity increased. The time distance between two particle bunches in a beam is reduced. As a result, the reconstructed momenta of the jets produced in each bunch crossing are significantly contaminated by multiple interactions. A dedicated technical approach has been developed for correcting the reconstructed jet momenta. The corrections have been calibrated and configured for the data taking in 2015 and 2016.Cette thèse présente une mesure de la section efficace de production de jets associés à un boson Z dans les collisions proton-proton du Grand Collisionneur de Hadron (LHC) situé au CERN, avec des énergies dans le centre de masse de 8 TeV et 13 TeV, respectivement pour les années 2012 et 2015. Les données utilisées pour cette analyse ont été collectées par le détecteur Compact Muon Solenoid (CMS). Elles constituent des échantillons de luminosités intégrées de 19.6 fb⁻¹ et 2.25 fb⁻¹, respectivement pour 2012 et 2015. Nous mesurons la section efficace différentielle en fonction de la multiplicité de jets, de l’impulsion transverse et de la rapidité des jets, et en fonction de la somme scalaire des impulsions transverses des jets. La corrélation entre les rapidités du boson Z et des jets est aussi mesurée et bénéficie de la large statistique prise en 2012. Toutes les distributions d’observables mesurées sont obtenues après corrections pour les effets détecteurs et les résultats des canaux de désintégration muonique et électronique du boson Z sont combinés. Tenant compte des incertitudes statistiques et systématiques, les mesures sont comparées à différentes prédictions théoriques ayant différents niveaux de précision. Les prédictions sont obtenues de MADGRAPH 5, SHERPA 2 (pour l’analyse à 8 TeV uniquement), MADGRAPH_AMC@NLO, et un modèle fixé au NNLO (pour l’analyse à 13 TeV uniquement). Par ces mesures de précisions, et en particulier celle de la corrélation de rapidités, nous avons acquis une compréhension plus approfondie de la chromodynamique quantique dans son régime perturbatif. Grâce à la plus haute énergie jamais atteinte en laboratoire, et à la grande statistique disponible, nous avons sondé avec précision des endroits de l’espace des phases jusque là inaccessibles.Dans cette thèse, les corrections et la calibration de l’énergie des jets pour le haut niveau de sélection de CMS est également présentée. Durant la période de 2012 à 2015, le LHC a été amélioré, non seulement l’énergie dans le centre de masse a augmenté, mais la luminosité instantanée a aussi été amplifiée. L’écart temporelle entre deux paquets de particules dans les faisceaux du LHC a été réduite. L’une des conséquences est que l’impulsion reconstruite pour les jets produits lors d’un croisement de faisceau à une contribution significative venant des multiples interactions ayant lieux lors du croisement des paquets. Une approche technique dédiée a été développée pour corriger l'impulsion des jets. Les corrections obtenues ont été calibrées aux données prises en 2015 et 2016.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Neveu, Jeremy. "Contraintes expérimentales sur des modèles à champ scalaire léger en cosmologie et physique des particules (expériences SNLS et CMS)." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066233/document.
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Face à la nature inconnue de l'énergie noire et de la matière noire, des modèles à champ scalaire léger ont été proposés pour expliquer l'accélération tardive de l'expansion de l'Univers et l'apparente abondance de matière non baryonique dans l'Univers. Dans une première partie, cette thèse confronte de la façon la plus précise possible les données de cosmologie les plus récentes au modèle du Galiléon, une théorie de gravité modifiée possédant des propriétés théoriques particulièrement intéressantes. Des contraintes observationnelles sur les paramètres du modèle sont dérivées en utilisant les dernières mesures liées aux distances cosmologiques et à la croissance des grandes structures de l'Univers. Un bon accord est observé entre les données et les prédictions théoriques, faisant du Galiléon un modèle alternatif compétitif avec celui de la constante cosmologique. Dans une seconde partie, la production de Branons, particules scalaires candidates au statut de matière noire venant d'une théorie de dimensions supplémentaires, est recherchée dans les collisions proton-proton enregistrées en 2012 par l'expérience Compact Muon Solenoid auprès du Grand Collisionneur de Hadrons. Des événements présentant un photon et de l'énergie transverse manquante dans l'état final sont sélectionnés dans les données et comparés aux estimations des bruits de fonds attendus. Aucun excès d'événements n'étant observé, des limites expérimentales sur les paramètres de la théorie du Branon sont calculées. Elles sont les plus contraignantes à ce jour. Cette thèse se conclut par des arguments pour une description unifiée des deux modèles étudiés, dans le cadre des théories de dimensions supplémentairesThe nature of dark energy and dark matter is still unknown today. Light scalar field models have been proposed to explain the late-time accelerated expansion of the Universe and the apparent abundance of non-baryonic matter. In the first part of this thesis, the Galileon theory, a well-posed modified gravity theory preserving the local gravitation thanks to the Vainshtein screening effect, is accurately tested against recent cosmological data. Observational constraints are derived on the model parameters using cosmological distance and growth rate of structure measurements. A good agreement is observed between data and theory predictions. The Galileon theory appears therefore as a promising alternative to the cosmological constant scenario. In the second part, the dark matter question is explored through an extra-dimension theory containing massive and stable scalar fields called Branons. Branon production is searched for in the proton-proton collisions that were collected by the Compact Muon Solenoid experiment in 2012 at the Large Hadron Collider. Events with a single photon and transverse missing energy are selected in this data set and compared to the Standard Model and instrumental background estimates. No signature of new physics is observed, so experimental limits on the Branon model parameters are derived. This thesis concludes with some ideas to reach an unified description of both models in the frame of extra-dimension theories
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Tschudi, Yohann. "Reconstruction de muons cosmiques en collision et recherche de gluinos se désintégrant en stop-top dans l'expérience CMS au LHC." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00640000.
Full textAbstract:
L'expérience CMS (Compact Muon Solenoid), construite sur l'anneau du LHC (Large Hadron Collider), enregistre des données provenant des collisions proton-proton depuis 2 ans. L'alignement entre toutes les couches du trajectographe, sous-détecteur de CMS permettant la reconstruction et la mesure de l'impulstion des particules chargées, est effectué à l'aide de traces de particules créées lors de la collision et des traces créées par le passage de muons d'origine cosmique à travers ce détecteur. La première partie de ce livre sera dédiée à la reconstruction des traces de ces muons lors des collisions. Une nouvelle méthode, appelée reconstruction cosmique régionale, a été développée et mise en place. L'efficacité de 69% et le taux de faux de l'ordre de 1% permettent l'utilisation de ces traces pour l'alignement. La deuxième partie, portant sur l'analyse des données de collision, s'intéressera à la recherche de particules prédites par un modèle d'extension du Modèle Standard, la Supersymétrie, dans un scénario particulier, le scénario du Stop Léger. Dans le cas d'un fort mélange dans la troisième génération de squarks, le stop, partenaire supersymétrique du quark top, peut être léger. Dans l'analyse effectuée au cours de cette thèse, nous nous sommes intéressés au cas au mstop < mtop. Dans le MSSM avec conservation de la R-parité, le gluino serait formé par paire et se désintégrerait en un squark stop et un quark top. Le stop se désintégrerait quant-à-lui en un quark c et un neutralino, particule supersymétrique la plus légère du modèle, stable et interagissant faiblement. Aucun excès par rapport aux prédictions du Modèle Standard n'a été relevé en utilisant les 40pb-1 de données enregistrées par CMS en 2010. Les limites obtenues à 95% de niveau de confiance permettent d'exclure des masses de stop jusqu'à 175 GeV pour des masses de gluinos allant jusqu'à 350 GeV et des faibles différences de masses entre le stop et le neutralino.
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Marionneau, Matthieu. "Etude des états finals à deux bosons Z dans le canal leptons-neutrinos dans l'expérience CMS auprès du LHC au CERN." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://tel.archives-ouvertes.fr/tel-00653498.
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Une étude des états finaux ZZ avec les premières données acquises par le détecteur CMS est présentée dans cette thèse. Cette étude exploite les premières données délivrées par le LHC et enregistrées par CMS en 2010 et 2011. La section efficace de production ZZ est mesurée et des limites sont posées sur deux constantes de couplages de jauge électrofaibles anomaux neutres. La présence de tels couplages serait une évidence de nouvelle physique au delà du Modèle Standard et nécessite d'être étudiée en détail. De plus, le processus de création de paire de boson Z dans le Modèle Standard est un bruit de fond pour la recherche du boson de Higgs et doit être connu avec précision. Une série d'études préalables est effectuée sur le calorimètre électromagnétique de CMS : ces études portent sur le système de lecture sélective et le système de contrôle laser. Une autre étude préalable porte sur le comportement et la mesure de l'énergie transverse manquante dans des événements contenant un boson électrofaible se désintégrant dans le canal électronique. Cette étude montre que l'empilement a un impact important sur la mesure de l'énergie transverse manquante et que des corrections doivent être déployées pour réduire ces effets. Les conclusions de ces analyses contribuent à la bonne compréhension des résultats obtenus sur les états finaux à deux boson Z.
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Boaretto, Juliana Fonseca. "Estudo do comportamento de variáveis cinemáticas na produção difrativa de mésons D-+* em colisões próton-próton √s = 7TeV." Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=4702.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorApresentamos um estudo preliminar da produção difrativa de mésons utilizando dados obtidos da colisão próton-próton, a energias de centro de massa de 7 TeV, com o experimento CMS-LHC. O trabalho inclui o desenvolvimento do algoritmo de reconstrução dos mésons D* através do canal de decaimento D*->D0 + pion (lento) ->K+pion, a medida da eficiência de detecção e reconstrução, e uma análise do comportamento de variáveis cinemáticas na produção difrativa dessas partículas, particularmente, das lacunas de rapidez. Para isso, foi utilizada uma luminosidade integrada de 3,171pb^(-1) de dados coletados no ano de 2010. As análises com os dados experimentais foram comparadas com os resultados obtidos com geradores de Monte Carlo PYTHIA6, PYTHIA8 e POMPYT.
In this work we present a very preliminary study of the diffractive production of mesons D* from proton-proton collisions, at center of mass energy of 7 TeV, with the CMS-LHC experiment. The decay channel where D*->D0 + pion (slow) ->K+pion was reconstructed and the efficiency was computed. An analysis of the dependence of the kinematical variables,particularly of the pseudo rapidity gap Δη, on the meson production was done. A total luminosity of 3.171pb^(-1) of data collected in the year of 2010 was analyzed, and the reconstructed data were compared to the ones obtained with PYTHIA6, PYTHIA8 and POMPYT generators.
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Panwar, Lata. "Searches for Higgs boson pair production in bbbb and bbgammagamma final states at Compact Muon Solenoid detector." Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5668.
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The discovery of the Higgs boson makes the Standard Model (SM) a promising theory to understand fundamental physics. Despite its progress, the theory does not explain many observed phenomena such as dark matter and hierarchy problems. This motivates us to go beyond the Standard Model (BSM). Furthermore, the Higgs self-coupling is rather weakly constrained by the current measurements and allows the possibility of new physics. As the latest discovered piece of the SM, the Higgs boson can be used to explore new physics models. There are novel BSM resonances that directly couple to Higgs boson and are easier to observe with direct searches. The thesis focuses on non-resonant and resonant di-Higgs searches at the Large Hadron Collider (LHC), where a pair of Higgs bosons get produced during proton-proton collisions.
In the first part of the work, we present di-Higgs searches at the high luminosity LHC (HL-LHC) in the final state of four bottom quarks at √s = 14 TeV. The study is performed using simulations of phase-2 Compact Muon Solenoid (CMS) detector assuming up to 200 proton-proton collisions within each bunch-crossing and 3 ab-1 total integrated luminosity. We start with the resonant di-Higgs production via vector boson fusion (VBF) in a boosted regime where resonance is a massive spin-2 bulk KK graviton particle predicted by the warped extra dimension model. This is the first CMS analysis that explores VBF resonant production mechanism. Both the Higgs bosons are required to be sufficiently Lorentz-boosted to reconstruct them as a large-area jet. The signal also contains two energetic VBF jets in the forward pseudorapidity regions of the detector. The unique topology of the production and decay would benefit from the upgraded phase-2 CMS detector having extended tracker coverage and a high granularity calorimeter which motivates this study. The SM multijet processes are the main background for the analysis. Expected signal significances for observing a bulk KK graviton, having a mass between 1.5–3.0 TeV and a width that is narrow up to 5%, are projected, assuming the signal cross-section to be 1 fb. Following a similar boosted strategy, non-resonant di-Higgs production for the SM and effective field theory (EFT) motivated shape benchmarks are also studied. A 95% confidence level (CL) upper limit on the product of Higgs boson pair production cross-section and branching fraction is presented for the benchmarks. The results show prospects of significant sensitivity for EFT motivated non-resonant di-Higgs production at the HL-LHC.
In the second part, we use 2016, 2017, and 2018 LHC run period data of the CMS detector at √s = 13 TeV with 138 fb-1 total integrated luminosity and present the study for resonant di-Higgs production via the gluon-gluon fusion in the final state of two photons and two bottom quarks in a resolved regime. The physics is motivated by the warped extra dimension model where spin-0/2 resonance decays into two Higgs bosons and the next-to-minimal supersymmetric model where spin-0 resonance decays into a Higgs boson and another spin-0 particle different from the discovered Higgs boson. It is the first analysis that explores an NMSSM motivated scenario in this final state. The diphoton decay mode of the Higgs boson benefits from the excellent energy resolution of the CMS electromagnetic calorimeter, which makes this channel the most sensitive one among the various di-Higgs decay modes. The analysis uses machine learning methods to reject dominating diphoton QCD background contamination. As a result, it enhances the analysis sensitivity despite having a low di-Higgs branching fraction channel. With the narrow-width approximation, a model-independent 95% CL upper limit on the product of resonant production cross-section and branching fraction is set for resonance mass up to 1 TeV. The results are also compared with appropriate BSM predictions to exclude allowed resonance mass ranges.
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Iorio, Alberto Orso Maria. "Measurement of single top t-channel production cross section through the t → W b → μνb decay in 7 TeV proton-proton collisions with the Compact Muon Solenoid detector at the Large Hadron Collider." Tesi di dottorato, 2011. http://www.fedoa.unina.it/8937/1/Iorio.pdf.
Full textAbstract:
In my PhD I actively participated the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) of CERN. My work over the three years of the PhD encompassed several aspects of the experiment, including participation to data taking activities, performance studies of the detector and data analysis finalized to the measurement of single top quark production. During the first year of my Ph.D. program I had the chance to participate in the commissioning effort of the CMS Muon System, studying the performances of the Resistive Plate Chambers detectors using cosmic ray data collected in 2008-2009 and early collision data taken in 2010. The second and third years of my Ph.D. program were devoted to the study of the production of single-top events in proton-proton collisions at LHC. The LHC has been successfully running since the end of 2009 and is
providing 7 TeV center of mass proton-proton collision data since March 2010, collecting data corresponding to an integrated luminosity of 36.1 inverse pb . With the data taking of 2011, the instantaneous luminosity of the machine was constantly upgraded, allowing to collect 5.73 inverse fb of integrated luminosity. The CMS detector has successfully collected collision data through 2010 and 2011, collecting a total integrated luminosity of 5.22 inverse fb . The LHC is often considered to be a “top quark factory”, allowing for a production of top quarks through several mechanisms: tt pair production, mainly occurring through processes which involve the strong interaction, and single top quark production, which occurs through electroweak interactions and has been object of study of my thesis. There are three mechanisms of production of single top, known as t,s, and tW channels. The study of single top processes provides the unique opportunity to explore the electroweak sector of top quark physics, allowing for example a direct measurement of Vtb as well as the study of Flavour Changing Neutral Currents. On the other hand single top channels offer a window for searches for physics beyond standard model, being for instance sensitive to W resonances. Amongst the three channels, I focused my work on the t channel, which yields a production cross section of 64.6 pb, the highest amongst the single top processes. I developed and deployed an analysis which focused on the top quark decay channel t → W b → μνb aiming at early observation of single top events with the 2010 dataset. I was successful in achieving the first experimental evidence of single top at the LHC, which resulted in a paper published on PRL . With 2011 data incoming, I developed and deployed a new analysis, adapting the strategy to a different goal: the new analysis should have minimized the systematic uncertainty and at the same time be model-independent to allow for further studies of single top polarization and beyond standard model physics searches. The results have been updated with a luminosity of 1299 inverse pb , and a combination with the electron channel results has been performed to increase the precision of the measurement.
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FROSALI, SIMONE. "Measurement of sigma(Z/gamma* + >= n jets) in the electronic channel with the CMS detector." Doctoral thesis, 2012. http://hdl.handle.net/2158/630095.
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Kopp, Gillian Baron. "Search for SUSY with Delayed Photons at the Compact Muon Solenoid." Thesis, 2018. https://thesis.library.caltech.edu/10924/1/Kopp_Gillian_2018.pdf.
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The Compact Muon Solenoid (CMS) experiment records data from proton-proton (pp) and heavy ion (Pb-Pb and Pb-p) collisions at the Large Hadron Collider (LHC) to search for physics beyond the Standard Model, test theories of supersymmetry (SUSY), and measure properties of known particles with higher precision. In 2025, the LHC will be upgraded to the High Luminosity LHC (HL-LHC), where the luminosity will be increased by a factor of 10. This will increase the number of pile-up collisions to 140-200 events per proton-proton bunch crossing, compared to the current 40 events per crossing (where each bunch crossing occurs every 25 ns). In order to fully exploit the sensitivity of the CMS experiment, the current detectors must be upgraded to mitigate the effects of the large number of pileup interactions expected in collisions at the HL-LHC. New capabilities, such as precision timing measurements in calorimetric devices and minimum ionizing detectors, have been shown to effectively mitigate the effects due to pileup, and are expected to benefit the overall physics reach of the experiment. In addition to mitigating pileup and increasing the detector capabilities, precision timing is beneficial in the search for particles beyond the Standard Model. A simulation of a benchmark long lived neutralino SUSY search is presented, and it is shown that the generator particle flight times can be faithfully reconstructed using the detector-level information. Identification algorithms for the SUSY model have been significantly improved with the use of a Boosted Decision Tree, and it is demonstrated that this algorithm has many benefits as compared to cut based IDs. With use of the BDT for the long lived neutralino SUSY model, the background rejection is increased significantly, with constant signal acceptance of 53.6%. This is an improvement in the significance of the signal selection by a factor of 2.38. Further improvement is seen with the inclusion of detector timing information in the BDT – with this contributing ≈25% of the information used in signal event identification. We thus demonstrate that with the BDT, the SUSY neutralino search can be performed with increased signal identification significance, and the searches’ sensitivity is expected to improve with the time resolution attained by the upgraded CMS calorimeter.
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Peña, Herrera Cristián. "Searches for New Physics at the Compact Muon Solenoid Experiment and Precision Timing Calorimetry." Thesis, 2017. https://thesis.library.caltech.edu/10189/7/thesis_cpena.pdf.
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In this thesis, we present several searches for beyond the standard model physics in proton-proton collisions recorded by the Compact Muon Solenoid Experiment at center-of-mass energy of 8 and 13\TeV. We search for particle dark matter in events with two or more jets and missing transverse momentum at $\sqrt{s} = 8$ TeV, in this search we use the razor variables to discriminate signal from background events and thus improve the overall sensitivity of the analysis. We observe agreement between the observation and the background estimation. The interpretation of the results is carried out in the context of an effective field theory that couples the standard model quarks to the dark matter candidate. A search for anomalous production of Higgs bosons using 15.3 $\mathrm{fb}^{-1}$ of proton-proton collisions at $\sqrt{s} = 13$ TeV is also presented; this search selects events with a Higgs boson in association with jets, where the Higgs candidate decays into two photons. We also employ the razor variables ($\mathrm{M_{R}}, \mathrm{R}^{2}$) to discriminate signal from background. We observe an excess of events in one of the search bins with relatively high values of $\mathrm{M_{R}}$ and $\mathrm{R}^{2}$. The interpretation of this analysis is pair production of bottom squarks in the context of supersymmetry, this model is also presented in one of the appendices of this thesis. In the other appendix of this thesis, we present a search for new phenomena in high-mass diphoton events using 12.9 $\mathrm{fb}^{-1}$ of proton-proton collisions at $\sqrt{s} = 13$ TeV. This search observed a significant excess (3.4 standard deviations, local) with 2015 data at a diphoton invariant mass of 750 GeV, equivalent to $\approx$ 20\% of the current dataset. By repeating the search with the larger dataset collected in 2016, we found that the aforementioned excess has been greatly disfavored. Additionally, in order to confirm the robustness and correctness of the data analysis techniques used in this search, we have carried out a second -- completely independent -- analysis, which confirms the absence of an excess at a diphoton invariant mass of 750 GeV.
We also present detector research and developments studies of electromagnetic calorimeters equipped with precision timing capabilities. We present several calorimeter prototypes that were tested at the Fermilab Test Beam Facility. These prototypes include LYSO-based calorimeters, tungsten-LYSO "shashlik" sampling calorimeters, micro-channel-plate sampling calorimeters, and silicon-based sampling calorimeters. The results of these studies indicate that time resolutions of the order of $\sim$ 30 ps are readily available when measuring electromagnetic showers. A discussion about the applications of precision timing in high energy physics experiments is also presented, with a particular interest in pileup rejection in the context of the high-luminosity upgrade of the Large Hadron Collider foreseen to start in 2025.
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Simon, Michał. "Fault tolerant data acquisition through dynamic load scheduling." Rozprawa doktorska, 2013. https://repolis.bg.polsl.pl/dlibra/docmetadata?showContent=true&id=21532.
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Simon, Michał. "Fault tolerant data acquisition through dynamic load scheduling." Rozprawa doktorska, 2013. https://delibra.bg.polsl.pl/dlibra/docmetadata?showContent=true&id=21532.
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