1,720,988 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
Peeking into the dark with the ATLAS detector
No full textAstrophysical and cosmological measurements consistently find a presence of dark matter in the universe with an abundance significantly exceeding that of the visible baryonic matter. Its nature, however, remains unknown. Theories beyond the Standard Model accommodate dark matter by considering a new dark sector interacting with the Standard Model particles via heavy mediators. The seminar presents results from a variety of recent ATLAS searches based on the full Run-2 dataset. These searches seek evidence for the production of dark matter, either in association with Standard Model particles (top quarks and vector bosons) or via semi-visible jets arising from a strongly coupled dark sector. In addition to searches for dark matter, the seminar also presents a recent milestone analysis on the search for long-lived particles using displaced energy deposits in the ATLAS calorimeters.</p
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
Searches for additional Higgs bosons in the MSSM by the ATLAS detector
No full textThe MSSM predicts the existence of additional neutral and charged Higgs bosons. This presentation will discuss results from recent searches for these particles in several decay channels based on collision data collected at 13 TeV, and their interpretation within the MSSM
Prompt signature searches in ATLAS
No full textMany new physics models predict the existence of feebly interacting particles. This talk summarizes recent searches for Beyond-the-Standard-Model resonances leaving prompt decays in the ATLAS detector using Run 2 data collected at the LHC
Measurements of tV and ttV production with ATLAS and CMS detectors.
No full textThe study of ttV and tV processes provides direct information off the electroweak couplings of the top to weak bosons. Deviations from the Standard Model predictions might indicate the presence of Beyond Standard Model physics in the EWK or top-quark sectors, either in the form of anomalous couplings, CP violating couplings or sizeable / spin asymmetry and/or spin correlations. In this talk, the latest precision measurements in ATLAS and CMS at = 13 TeV of the associated production of Z, W or bosons with or single- are presented
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
Measurements of ttbar pairs produced in association with electroweak gauge bosons using the ATLAS detector
No full textThe large centre-of-mass energy available at the proton-proton collider LHC allows for the copious production of top-quark-antiquark pairs in association with electroweak gauge bosons (W / Z / gamma) at high transverse momenta. The tt ̄Z and tt ̄W production cross sections are simultaneously measured using a combined fit in several analysis regions. The measurement of the tt ̄Z cross section is used to set constraints on effective field theory operators which modify the tt ̄Z vertex. The ttgamma measurements are performed in single-lepton and dilepton final states in a fiducial volume. The differential cross-sections are measured as a function of several photon kinematic variables
Contribution à la mesure d'énergie et du temps des électrons et des photons dans l'expérience ATLAS et recherche de la production de matière noire en association avec un boson de Higgs
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 depend 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 has been put in place in topologies containing a Higgs boson decaying into two photons.La découverte d'une particule cohérent avec la production d'un boson de Higgs du Modèle Standard (MS) en 2012 par les collaborations ATLAS et CMS a ouverte de nouvelles possibilités de recherche de physique au-delà du MS (BSM). Les recherches de matière noire en ATLAS se concentrent sur des modèles générales, appelées mono-X, qui prédisent la production d'un seul objet X (jet, photon ou des bosons W ou Z) en association à des particules de matière noire (DM). La production de ces états finaux dépend du couplage entre les objets radiés et les particules en collision. Ce fait encourage la recherche des signaux mono-Higgs car le boson de Higgs ne se couple pas directement avec des gluons et ses couplages avec les quarks légères sont très faibles. Par conséquent, le Modèle Standard ne prédit pas une grande contribution à ces états finaux, donc toute déviation observée des prédictions du MS permettrait d'étudier directement le couplage du boson de Higgs à des nouveaux secteurs BSM. Lors de cette thèse, une recherche a été menée sur la production des particules de matière noire en association à un boson de Higgs se désintégrant en deux photons. En ayant pour but d'augmenter la sensibilité de l'expérience à une possible découverte, des études sur l'effet de diaphonie ont été menées afin d'améliorer l'identification de photons dans ATLAS. Par ailleurs, les particules de matière noire n'interagissent pas avec le détecteur, ce qui impose des signatures avec une grande énergie transverse manquante. Des études sur la performance de la reconstruction de cette énergie transverse manquante ont été mises en place pour des topologies contenant un boson de Higgs se désintégrant en deux photons
- …
