1,721,134 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Recherche de matière noire produite en association avec un boson de Higgs avec les données à 13 tev de l'expérience ATLAS et évaluation des performances du détecteur de temps à haute granularité
No full textLes preuves accablantes de l'existence de matière noire dans l'univers présentées par les observations astrophysiques et cosmologiques motivent le programme de recherche de matière noire candidate aux expériences du LHC.Si ces nouvelles particules peuvent être produites lors de collisions proton-proton au LHC, elles apparaîtront comme des signatures d'impulsion transverse manquantes en raison de leur faible interaction avec la matière baryonique.La découverte d'un boson de Higgs sur ATLAS et CMS en 2012 a ouvert de nouvelles possibilités pour rechercher des candidats de matière noire produits en association avec un boson de Higgs. Cette thèse présente deux analyses basées sur l'ensemble de données ATLAS Run 2 de 139 fb-1, à la recherche de candidats de matière noire produits en association avec une particule de Higgs. Dans les deux analyses, le boson de Higgs est reconstruit exclusivement dans le canal diphoton.La signature Mono-Higgs est basée sur une particule de médiateur, reliant le modèle standard au secteur sombre, montrant un boson de Higgs et des particules de matière noire à l'état final.La recherche d'une production electroweakino recherche un boson de Higgs, un boson W et un moment transversal manquant à l'état final.Cette thèse contient également des études de performance approfondies réalisées pour le détecteur de temps hautement granulaire, un projet de mise à jour d'ATLAS.Les informations de temps de haute précision de 30 à 50 ps par trace fournies par ce détecteur ouvrent de nouvelles stratégies pour l'atténuation de l'empilement, qui sont basées sur une bonne capacité de reconstruction de temps de piste.The overwhelming evidence for the existence of dark matter in the universe presented by astrophysical and cosmological observations motivates the search program for dark matter candidates at the LHC experiments.If these new particles can be produced in proton-proton collisions at the LHC, they would appear as missing transverse momentum signatures due to their weak interaction with baryonic matter.Additionally, the discovery of a Higgs boson at both ATLAS and CMS in 2012 opened new possibilities to search dark matter candidates produced in association with a Higgs boson. This thesis presents two analyses based on the full ATLAS Run 2 dataset of 139 fb-1 recorded between 2015 and 2018, searching for dark matter candidates produced in association with a Higgs particle. In both analyses, the Higgs boson is reconstructed exclusively in the diphoton channel.The Mono-Higgs signature is based on a mediator particle, connecting the Standard Model with the dark sector, showing a Higgs boson and dark matter particles in the final state.The search for electroweakino production looks for a Higgs boson, a W boson and missing transverse momentum in the final state.This thesis also contains extensive performance studies performed for the High-Granularity Timing Detector, an ATLAS upgrade project that will be installed in the ATLAS cavern before the start of the High-Luminosity LHC runs in 2027.The high precision timing information of 30 - 50 ps per track provided by this detector opens up new strategies for pile-up mitigation, which are based on a good track-time reconstruction capability.An in depth assessment of first reconstruction algorithms and the posed challenges is provided
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Contribution to the energy and time measurement of electrons and photons in the ATLAS experiment and search for dark matter production in association to a Higgs boson.
No full textThe discovery of a particle consistent with a Standard Model (SM) Higgs boson in 2012 by the ATLAS and CMS collaborations has opened up new possibilities in searches for physics beyond the SM (BSM). Searches for dark matter in ATLAS focus on a special case of general models called, mono-X, that predict a single object X (jet, photon, W or Z bosons) produced in association to dark matter (DM) particles. The production of these final states depends on the coupling between the radiated object and the colliding particles. This fact motivates the search of mono-Higgs signals since Higgs does not couple to gluons and its couplings to light quarks are very weak. Then, the Standard Model does not predict a large contribution to these mono-Higgs final states, thus any deviation from SM predictions is a direct probe of a coupling between the Higgs and a new BSM sector. A search of DM particles produced in association to a Higgs boson decaying into two photons has been carried out in this thesis. Aiming to increase the significance of discovery in this channel, studies on the cross-talk effect has been performed to improve photon identification in ATLAS. Besides, DM particles are not expected to interact within the detector fiducial volume, thus predicted signatures include a large missing transverse momentum. Performance studies of the reconstruction of this missing momentum have been put in place in topologies containing a Higgs boson decaying into two photons. No significant excess has been found and 95 % confidence level limits are set on the observed signal. Additionally, the results are interpreted in terms of 90 % confidence-level limits on the spin-independent dark matter-nucleon cross-section as a function of the dark matter particle mass
Searching for Axion-Like-Long-Lived-Particles at the ATLAS experiment and a contribution to the Madanalysis5 recasting framework
No full textLa matière noire constitue environ 27 % du contenu énergétique de l'univers, posant l'une des questions les plus profondes de la physique moderne. De nombreuses théories au-delà du Modèle Standard (BSM) proposent divers candidats et médiateurs pour la matière noire, les axions et les particules de type axion (ALPs) étant des exemples importants. Les ALPs, à travers des descriptions en théorie effective des champs, présentent souvent de longues durées de vie, conduisant à des particules de longue durée de vie (LLPs). Ces LLPs génèrent des signaux distincts dans les expériences de collisionneurs comme ATLAS et CMS, défiant les algorithmes d'identification et de reconstruction conventionnels. Cette thèse se concentre sur le développement de techniques novatrices basées sur le calorimètre pour détecter les ALPs se désintégrant en paires de photons dans le détecteur ATLAS, en abordant les défis uniques posés par les signaux déplacés et en augmentant la sensibilité aux recherches de LLP.En plus de se concentrer principalement sur les recherches de matière noire et de LLP, ce travail inclut des contributions significatives au cadre MadAnalysis 5 pour la réinterprétation des recherches de violation de la parité R de la SUSY par ATLAS. En intégrant des modèles de machine learning (ML) basés sur ONNX dans MadAnalysis, le cadre prend désormais en charge efficacement la recast des analyses basées sur le ML. Ce développement facilite la reproduction et la réinterprétation précises des analyses complexes, assurant des performances cohérentes dans différents environnements. En outre, la thèse détaille les avancées en technologie des détecteurs de pixels grâce aux campagnes de test-beam ITk menées en 2022. Ces campagnes ont évalué les performances des capteurs, atteignant des efficacités de détection dépassant 99 %. Les connaissances acquises ont été cruciales pour établir de meilleurs logiciels de reconstruction et workflows garantissant la cohérence des résultats. Ces améliorations sont significatives pour le projet ITk et la phase de mise à niveau du LHC vers une machine à haute luminosité. Dans l'ensemble, cette thèse présente une approche complète pour faire progresser la recherche sur la matière noire grâce à des techniques innovantes de détection des LLP, des capacités de réinterprétation améliorées pour les analyses basées sur le ML et des contributions significatives au développement de la technologie des détecteurs.Dark Matter constitutes approximately 27% of the universe's energy content, posing one of the most profound questions in modern physics. Numerous Beyond Standard Model (BSM) theories propose various candidates and mediators for dark matter, with axions and axion-like particles (ALPs) being prominent examples. ALPs, through effective field theory descriptions, often exhibit long lifetimes, leading to long-lived particles (LLPs). These LLPs generate distinct signals in collider experiments like ATLAS and CMS, challenging conventional identification and reconstruction algorithms. This thesis focuses on developing novel calorimeter-based techniques to detect ALPs decaying into photon pairs within the ATLAS detector, addressing the unique challenges posed by displaced signals and enhancing the sensitivity of LLP searches. In addition to the primary focus on dark matter and LLP searches, this work includes significant contributions to the MadAnalysis 5 framework for the reinterpretation of ATLAS SUSY R-parity violation searches. By integrating ONNX-based machine learning models into MadAnalysis, the framework now supports efficient Machine Learning (ML)-based analysis recasting. This development facilitates the accurate reproduction and reinterpretation of complex analyses, ensuring consistent performance across different environments. Furthermore, the thesis details the advancements in pixel detector technology through the ITk test-beam campaigns conducted in 2022. These campaigns evaluated sensor performance, achieving detection efficiencies exceeding 99%. The insights gained were crucial in establishing better reconstruction software and workflows to guarantee consistency in results. These improvements are significant for the ITk project and the upgrade phase of the LHC towards a high-luminosity machine. Overall, this thesis presents a comprehensive approach to advancing dark matter research through innovative LLP detection techniques, enhanced recasting capabilities for ML-based analyses, and significant contributions to detector technology development
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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