Global ETD Search

11	Reconstrução de energia para calorímetros finamente segmentados / Energy reconstruction for finely segmented calorimeters Peralva, Bernardo Sotto-Maior 11 September 2015 (has links) Submitted by Renata Lopes (renatasil82@gmail.com) on 2015-12-16T13:33:15Z No. of bitstreams: 1 bernardosottomaiorperalva.pdf: 8631621 bytes, checksum: e4e7f3d592c91e719474b259727bab6c (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2015-12-16T15:15:06Z (GMT) No. of bitstreams: 1 bernardosottomaiorperalva.pdf: 8631621 bytes, checksum: e4e7f3d592c91e719474b259727bab6c (MD5) / Made available in DSpace on 2015-12-16T15:15:06Z (GMT). No. of bitstreams: 1 bernardosottomaiorperalva.pdf: 8631621 bytes, checksum: e4e7f3d592c91e719474b259727bab6c (MD5) Previous issue date: 2015-09-11 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Esta tese apresenta técnicas de processamento de dados para a detecção de sinais e estimação de energia usando calorimetria de altas energias. Os calorímetros modernos possuem milhares de canais de leitura e operam sob alta taxa de eventos. Tipicamente, a reconstrução da energia envolve etapas de detecção e estimação, e é baseada na medida da amplitude do sinal (digitalizado) recebido. Os métodos empregados, atualmente, em experimentos de altas energias são baseados em técnicas de minimização da variância e selecionam os sinais de interesse a partir da estimação da energia. Este trabalho explora o uso de filtros casados para a detecção de sinais e faz uso de uma calibração para a estimação da energia dos sinais. Na abordagem proposta, os parâmetros aleatórios do pulso processado (fase e deformação) e a estatística do ruído de fundo são considerados no projeto do filtro digital, aumentando seu desempenho. No caso particular de experimentos onde a probabilidade de empilhamento de sinais é alta, uma outra solução, baseada na desconvolução linear de sinais para estimação de energia, é discutida. As técnicas propostas nesta tese foram implementadas offline e aplicadas no calorímetro de telhas (TileCal) do ATLAS no LHC. Foram utilizados sinais simulados, assim como dados reais adquiridos durante a operação nominal do LHC. Os estimadores propostos apresentaram menor erro quando comparados aos métodos empregados em calorímetros modernos e estão, atualmente, sendo validados para serem utilizados no TileCal. / This thesis presents data processing techniques of signal detection and energy estimation for high energy calorimetry. Modern calorimeters have thousands of readout channels and operate at high event rate conditions. Typically, the energy reconstruction involves both detection and estimation tasks, and it is based on the amplitude estimation of the received digitized signal. The current methods employed by high energy experiments are based on variance minimization techniques, and the valid signals are selected based on the energy estimation. This work explores the use of a technique based on Matched Filter for signal detection, and it makes use of a calibration factor to estimate the energy. In the proposed approach, the stochastic parameters of the pulse (phase and deformation) and the statistics from the background are considered for the filter design in order to increase performance. In particular cases, where the signal pile-up is likely to occur, another promising technique, based on linear signal deconvolution is discussed. The techniques proposed in this thesis were implemented offline and applied on the ATLAS Tile Calorimeter (TileCal) at LHC. Both simulated signals and real data acquired during nominal LHC operation were used. The proposed estimators presented smaller error with respect to the methods currently used in modern calorimeter systems, and they have been extensively tested to be used in TileCal. CNPQ::ENGENHARIAS::ENGENHARIA ELETRICA Detecção e Estimação de Sinais Filtro Casado Empilhamento de Sinais Física de Altas Energias Signal Detection and Estimation Matched Filter Signal Pile-up High Energy Physics
12	Reconstrução de energia em calorímetros operando em alta luminosidade usando estimadores de máxima verossimilhança / Reconstrution of energy in calorimeters operating in high brigthness enviroments using maximum likelihood estimators Paschoalin, Thiago Campos 15 March 2016 (has links) Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2016-08-12T11:54:08Z No. of bitstreams: 1 thiagocampospaschoalin.pdf: 3743029 bytes, checksum: f4b20678855edee77ec6c63903785d60 (MD5) / Rejected by Adriana Oliveira (adriana.oliveira@ufjf.edu.br), reason: Isabela, verifique que no resumo há algumas palavras unidas. on 2016-08-15T13:06:32Z (GMT) / Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2016-08-15T13:57:16Z No. of bitstreams: 1 thiagocampospaschoalin.pdf: 3743029 bytes, checksum: f4b20678855edee77ec6c63903785d60 (MD5) / Rejected by Adriana Oliveira (adriana.oliveira@ufjf.edu.br), reason: separar palavras no resumo e palavras-chave on 2016-08-16T11:34:37Z (GMT) / Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2016-12-19T13:07:02Z No. of bitstreams: 1 thiagocampospaschoalin.pdf: 3743029 bytes, checksum: f4b20678855edee77ec6c63903785d60 (MD5) / Rejected by Adriana Oliveira (adriana.oliveira@ufjf.edu.br), reason: Consertar palavras unidas no resumo on 2017-02-03T12:27:10Z (GMT) / Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-02-03T12:51:52Z No. of bitstreams: 1 thiagocampospaschoalin.pdf: 3743029 bytes, checksum: f4b20678855edee77ec6c63903785d60 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-02-03T12:54:15Z (GMT) No. of bitstreams: 1 thiagocampospaschoalin.pdf: 3743029 bytes, checksum: f4b20678855edee77ec6c63903785d60 (MD5) / Made available in DSpace on 2017-02-03T12:54:15Z (GMT). No. of bitstreams: 1 thiagocampospaschoalin.pdf: 3743029 bytes, checksum: f4b20678855edee77ec6c63903785d60 (MD5) Previous issue date: 2016-03-15 / Esta dissertação apresenta técnicas de processamento de sinais a ﬁm de realizar a Estimação da energia, utilizando calorimetria de altas energias. O CERN, um dos mais importantes centros de pesquisa de física de partículas, possui o acelerador de partículas LHC, onde está inserido o ATLAS. O TileCal, importante calorímetro integrante do ATLAS, possui diversos canais de leitura, operando com altas taxas de eventos. A reconstrução da energia das partículas que interagem com este calorímetro é realizada através da estimação da amplitude do sinal gerado nos canais do mesmo. Por este motivo, a modelagem correta do ruído é importante para se desenvolver técnicas de estimação eﬁcientes. Com o aumento da luminosidade (número de partículas que incidem no detector por unidade de tempo) no TileCal, altera-se o modelo do ruído, o que faz com que as técnicas de estimação utilizadas anteriormente apresentem uma queda de desempenho. Com a modelagem deste novo ruído como sendo uma Distribuição Lognormal, torna possível o desenvolvimento de uma nova técnica de estimação utilizando Estimadores de Máxima Verossimilhança (do inglês Maximum Likelihood Estimator MLE), aprimorando a estimação dos parâmetros e levando à uma reconstrução da energia do sinal de forma mais correta. Uma nova forma de análise da qualidade da estimação é também apresentada, se mostrando bastante eﬁciente e útil em ambientes de alta luminosidade. A comparação entre o método utilizado pelo CERN e o novo método desenvolvido mostrou que a solução proposta é superior em desempenho, sendo adequado o seu uso no novo cenário de alta luminosidade no qual o TileCal estará sujeito a partir de 2018. / This paper presents signal processing techniques that performs signal detection and energy estimation using calorimetry high energies. The CERN, one of the most important physics particles research center, has the LHC, that contains the ATLAS. The TileCal, important device of the ATLAS calorimeter, is the component that involves a lot of parallel channels working, involving high event rates. The reconstruction of the signal energy that interact with this calorimeter is performed through estimation of the amplitude of signal generated by this calorimter. So, accurate noise modeling is important to develop eﬃcient estimation techniques. With high brightness in TileCal, the noise model modiﬁes, which leads a performance drop of estimation techniques used previously. Modelling this new noise as a lognormal distribution allows the development of a new estimation technique using the MLE (Maximum Like lihood Estimation), improving parameter sestimation and leading to a more accurately reconstruction of the signal energy. A new method to analise the estimation quality is presented, wich is very eﬀective and useful in high brightness enviroment conditions. The comparison between the method used by CERN and the new method developed revealed that the proposed solution is superior and is suitable to use in this kind of ambient that TileCal will be working from 2018. CNPQ::ENGENHARIAS::ENGENHARIA ELETRICA Detecçãoe estimação de sinais Distribuição Lognormal Estimador de máxima verossimilhança Empilhamento de sinais Física de altas energias Signal detection and estimation Lognormal distribuition Maximum likelihood estimators Signal pile-up High energy physics
13	Investigations of calorimeter clustering in ATLAS using machine learning Niedermayer, Graeme 11 January 2018 (has links) The Large Hadron Collider (LHC) at CERN is designed to search for new physics by colliding protons with a center-of-mass energy of 13 TeV. The ATLAS detector is a multipurpose particle detector built to record these proton-proton collisions. In order to improve sensitivity to new physics at the LHC, luminosity increases are planned for 2018 and beyond. With this greater luminosity comes an increase in the number of simultaneous proton-proton collisions per bunch crossing (pile-up). This extra pile-up has adverse effects on algorithms for clustering the ATLAS detector's calorimeter cells. These adverse effects stem from overlapping energy deposits originating from distinct particles and could lead to difficulties in accurately reconstructing events. Machine learning algorithms provide a new tool that has potential to improve clustering performance. Recent developments in computer science have given rise to new set of machine learning algorithms that, in many circumstances, out-perform more conventional algorithms. One of these algorithms, convolutional neural networks, has been shown to have impressive performance when identifying objects in 2d or 3d arrays. This thesis will develop a convolutional neural network model for calorimeter cell clustering and compare it to the standard ATLAS clustering algorithm. / Graduate Machine Learning Artificial Neural Network Convolutional Neural Network Calorimetry Particle Physics ATLAS LHC ANN CNN Topological Clustering Particle Detector CERN Energy Depositions Pile-Up High Luminosity Residual Neural Network Large Hadron Collider HL-LHC
14	Recherche de nouvelles résonances se désintégrant en paires de quarks top avec le détecteur ATLAS du LHC / Search of new resonances decaying into top quark pairs with the ATLAS detector at the LHC and jet calibration studies Camacho Toro, Reina Coromoto 13 July 2012 (has links) (...) Le travail de recherche exposé dans cette thèse a été réalisé en utilisant les données collectées par le détecteur ATLAS auprès du LHC. Le LHC est l'accélérateur de particules le plus grand et le plus puissant jamais construit. Il est constitué d'un double anneau de stockage de protons. Environ 10000 physiciens et ingénieurs du monde entier participent à cette expérience en développant de nouvelles techniques et approches pour identifier les événements intéressants cachés dans l'environnement complexe produit dans des collisions proton-proton. Les premières collisions proton-proton ont eu lieu à la fin de l'année 2009 à une énergie de 900~GeV dans le système du centre de masse. Le 19 Mars 2010, le LHC a battu un record en augmentant l'énergie des faisceaux à 3.5 TeV, et les premières collisions à 7 TeV ont été enregistrées le 30 Mars 2010. L'énergie par faisceau pour l'ensemble de 2011 était de 3.5 TeV, et 4 TeV en 2012. Un an d'arrêt technique est prévu en 2013 avant de parvenir à l'énergie nominale de collision de 14 TeV. Quatre expériences se partagent les quatre points de croisement des faisceaux du grand anneau du LHC. Une d'entre elles, ATLAS, est un détecteur généraliste avec un vaste programme de physique. ATLAS est constitué d'un détecteur interne de traces dans un champ magnétique de 2 T, offrant une couverture jusqu'à \|η\|<2.5, un système calorimétrique allant jusqu'à \|η\|<4.9, un spectromètre à muons dans un champ magnétique toroïdal et un système de déclenchement composé de trois niveaux. Tous les sous-systèmes ont d'excellentes performances en termes d'efficacité et de résolution. Cette thèse comprend trois travaux interconnectés. En premier lieu, elle décrit les résultats de la recherche de nouvelles résonances qui se désintègrent en paires tt en utilisant les premiers 2.05 fb-1 de données collectées par le détecteur ATLAS en 2011. Dans une deuxième partie, en connection avec cette recherche, des études de performance de Jet Vertex Fraction (JVF) en utilisant des événements tt sont également présentées. JVF est une variable qui peut être utilisée pour réduire les effets d'empilement afin d'améliorer la précision et la sensibilité des analyses de physique à haute luminosité. Finalement, les performances de la calibration Globale Séquentielle des jets, sa validation sur des données réelles et l'évaluation de l'incertitude systématique qui lui est associée seront aussi discutées. La détermination précise de l'échelle en énergie des jets (JES: acronyme de Jet Energy Scale) ainsi que l'obtention d'une résolution optimale sont extrêmement importantes pour de nombreuses analyses de physique au LHC. Cela est vrai en particulier pour la recherche de nouvelles résonances tt en raison de la présence de jets dans l'état final. Les résultats sont présentés dans l'ordre dans lequel ils ont été réalisés au cours de cette thèse. (...) / (...) The studies presented in this thesis were performed using data collected by the ATLAS detector at the LHC. The LHC is the largest and highest energy particle accelerator ever built. Around 10000 physicists and engineers around the world are taking part in this experience by developing new techniques and approaches to identify the interesting physics buried in the complex environment produced in the LHC pp collisions. The LHC produced its first pp collisions on November 23, 2009 at the injection energy of 450 GeV. On March 19, 2010 the LHC broke a record by raising the beam energy to 3.5 TeV, and the first pp collisions at 7 TeV were recorded on March 30, 2010. The beam energy for the whole 2011 year was 3.5 TeV per beam, while in 2012 the beam energy is 4 TeV. At the beginning of 2013 the LHC will go into a long shutdown to prepare for higher energy collisions starting in 2014. At the four collision points of the LHC, detectors have been placed to study the high-energy collisions. One of these detectors, ATLAS, a general purpose detector with an extensive initial physics program. The ATLAS detector consists of a tracking system in a 2 T solenoid field, providing coverage up to a pseudo-rapidity of \|η\|<2.5, sampling electromagnetic and hadronic calorimeters up to \|η\|<4.9, muon chambers in a toroidal magnetic field and a trigger system consisting of three levels of event selection. So far, the ATLAS sub-detectors have shown an excellent performance in terms of efficiency and resolution. This thesis contains three different analyses interconnected. The main one concerns the results of the search for new resonances that decay to top-quark pairs using the first 2.05 fb-1 of data collected by the ATLAS detector in 2011. Secondly and related to this search, performance studies of the Jet Vertex Fraction (JVF) in top-quark pairs topologies are presented too. JVF is a variable that can be used to reduce the pile-up effects to improve the precision and sensitivity of physics analyses at high luminosities. Finally, results regarding the performance, validation in data and associated systematic uncertainty derivation of the Global Sequential (GS) jet calibration are discussed. The determination of the jet energy scale and the achievement of the optimal jet performance is of key importance to many LHC physics analyses, specially to the main analysis of this thesis due to the presence of jets in the final state. The results are presented in order that they were performed during the thesis. ATLAS LHC Quark top Calibration des jets Calibration Globale Séquentielle Résonances top-antitop Gluon Kaluza-Klein Topcolor Z' Jet Vertex Fraction Empilement ATLAS LHC Top quark Jet calibration Global Sequential calibration Resonances top-antitop Kaluza-Klein gluon Leptophobic topcolor Z' Jet Vertex Fraction Pile-up
15	Recherche de sgluons dans des états finals multitops avec le détecteur ATLAS auprès du LHC à √s = 8 TeV / Search for sgluons in multitop final states with the Atlas detector at the LHC at √s = 8 TeV Valéry, Loïc 30 June 2014 (has links) En dépit de nombreuses confirmations expérimentales, le Modèle Standard, théorie décrivant les particules élémentaires et trois des interactions fondamentales souffre de difficultés théoriques et expérimentales. Ces dernières motivent l’existence d’une physique non décrite jusqu’alors : la Nouvelle Physique. Ce travail se focalise sur la recherche de gluons scalaires, appelés communément sgluons, nouvelles particules prédites dans plusieurs théories de Nouvelle Physique. Une étude phénoménologique considère les différents états finals (de un à quatre quarks top) et signatures (un ou deux leptons chargés) qui peuvent être engendrés par l’existence de sgluons. La sensibilité d’une expérience comme Atlas à ce signal est estimée et montre que l’un des états finals les plus prometteurs est celui contenant quatre quarks top, dans la signature à deux leptons porteurs de la même charge électrique (électron ou muon). La recherche de sgluons dans l’expérience Atlas s’appuie sur les états finals à quatre quarks top dans une signature à deux leptons porteurs de la même charge électrique, des jets étiquetés b et de l’énergie transverse manquante. Elle représente la première recherche mondiale de sgluons dans cet état final. Les principaux enjeux de l’analyse (estimation des bruits de fond, optimisation de la sélection, interprétation statistique) sont détaillés. La comparaison avec les données enregistrées pendant la première partie de l’année 2012 (L = 14:3 fb..1) ne montre pas d’excès significatif. La limite inférieure sur la masse du sgluon est alors de 0.80+0:02..0:03 TeV. L’extension de cette analyse avec le lot complet de données enregistrées en 2012 par Atlas est également présentée dans ce document et permet une sensibilité accrue jusqu’à des masses de sgluons de 0:94 0:03 TeV. Ce document présente également les analyses et résultats relatifs à des études de performances. La première s’attache au système de hautes tensions du calorimètre hadronique à tuiles du détecteur Atlas (TileCal). Elle conclut notamment, au regard des critères établis, que seuls 7 canaux de hautes tensions du TileCal (sur un total de 9852) ont un comportement problématique. La deuxième étude est liée à la réjection de l’effet d’empilement au moyen d’une sélection sur la variable JVF (Jet Vertex Fraction). L’efficacité de cette sélection, calculée dans les données et dans la simulation montre des différences, nécessitant l’apport d’une correction à la simulation. La détermination de facteurs correctifs et de leurs incertitudes systématiques associées est présentée dans ce document. / Despite its experimental confirmations, the Standard Model, which describes both the elementary particles and three of the fundamental interactions, has some theoretical and experimental limitations. As a consequence of these limitations, a Physics not described in the context of the Standard Model could exist : the New Physics. This work focuses on the search for scalar gluons, commonly dubbed sgluons, predicted in various New Physics theories. A phenomenological study considers various final states (containing between two and four top quarks) and signatures (with one or two charged leptons) that could arise from sgluon production. The sensitivity of an Atlas-like experiment to this signal is estimated and the results indicate that one of the most promising final states contains four top quarks in a signature with two charged leptons (electron or muon) of the same electric charge. The search for sgluons within the Atlas experiment uses the previous results. Thus, it only investigates the 4-top topology in a signature containing two same-sign charged leptons, b-jets and missing transverse energy. It represents the first search ever for sgluons in this final state. The main steps of the analysis (background estimation, selection optimisation and statistical interpretation) are detailed. The comparison with the data recorded in the first months of 2012 (L = 14:3 fb..1) shows no significant excess and is interpreted in terms of a limit on the sgluon mass. The latter is found to be 0.80+0:02..0:03 TeV. The extension of this analysis to the full 2012 Atlas dataset is also presented in this document and shows an increased expected sensitivity to sgluon masses up to 0:94 0:03 TeV. Finally, this document also presents the analyses and results of performance studies. The first one is related to the high voltage system of the Atlas Tile Calorimeter (TileCal). The main conclusion is that only 7 channels out of the 9852 TileCal ones are fond to be problematic. The second study focuses on the rejection of the pile-up effect by the means of a selection applied on the so-called JVF (Jet Vertex Fraction) variable. The efficiency of this selection is computed both in data and simulation and shows some differences that have to be corrected in the simulation. The derivation of the correction factors and their associated systematic uncertainties is detailed in this document. Modèle Standard Nouvelle Physique Sgluons ATLAS LHC Calorimètre hadronique à tuiles TileCal Hautes tensions Effet d’empilement Jet Vertex Fraction JVF Leptons de même signe Événements à 4 quarks top Standard Model New Physics Sgluons ATLAS LHC Hadronic tile calorimeter TileCal High voltage Pile-up Jet Vertex Fraction JVF Same-sign leptons 4-top events
16	Nanolithography on thin films using heated atomic force microscope cantilevers Saxena, Shubham 01 November 2006 (has links) Nanotechnology is expected to play a major role in many technology areas including electronics, materials, and defense. One of the most popular tools for nanoscale surface analysis is the atomic force microscope (AFM). AFM can be used for surface manipulation along with surface imaging. The primary motivation for this research is to demonstrate AFM-based lithography on thin films using cantilevers with integrated heaters. These thermal cantilevers can control the temperature at the end of the tip, and hence they can be used for local in-situ thermal analysis. This research directly addresses applications like nanoscale electrical circuit fabrication/repair and thermal analysis of thin-films. In this study, an investigation was performed on two thin-film materials. One of them is co-polycarbonate, a variant of a polymer named polycarbonate, and the other is an energetic material called pentaerythritol tetranitrate (PETN). Experimental methods involved in the lithography process are discussed, and the results of lithographic experiments performed on co-polycarbonate and PETN are reported. Effects of dominant parameters during lithography experiments like time, temperature, and force are investigated. Results of simulation of the interface temperature between thermal cantilever tip and thin film surface, at the beginning of the lithography process, are also reported. Characterization Deflection Setpoint Grain rearrangement Array Precise positioning Metrology Explosion Explosives Data storage Material Image processing Slow scan disabled Temperature Tip Local In-situ Nanoscale Electrical circuit fabrication Repair Co-polycarbonate Polymers Polycarbonates Energetic materials PETN Simulation Interface Nano-manufacturing Experiment Calibration Raman Frequency Deflagration Decomposition Detonation Build up Pile-up End capped End capping Cross linked Cross-linked Conductivity Microscale MEMS Microcantilever NEMS DPN tDPN Silicon Glass Peak InVOLS Manipulation AFM Atomic force microscope Defense Nanoscale Surface Stiffness Force Scan size Thermal cantilevers Imaging Lithography Nanolithography Thin films Cantilevers Heaters Technology Nanotechnology Scan velocity Scan rate Bake Anneal Pentaerythritol tetranitrate Thin films Thermal properties Atomic force microscopy Microlithography Nanotechnology Surfaces (Technology) Analysis

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