1,720,954 research outputs found
Search for charged-lepton flavour violation in top-quark interactions using eµ final states with the ATLAS detector
Get PDFA search for charged-lepton-flavour violation in top-quark production and decay is presented.
The data analysed corresponds to 139 inverse femtobarns of proton-proton collisions at a centre-of-mass energy of 13 TeV delivered by the LHC and recorded by the ATLAS detector.
Two processes are studied; the first is the production of a semileptonically decaying single top quark in association with a pair of opposite-sign different-flavour leptons, the second is the production of a top-quark pair, where one top quark decays into a pair of opposite-sign different-flavour leptons and a light up-type quark, while the other decays into a leptonically decaying W boson and a b-quark according to the Standard Model.
The signal signature requires the presence of three leptons defined as electrons or muons,
and is thus characterised by the presence of one b-jet, up to one light-quark jet, and either two electrons and one muon, or one electron and two muons.
In the absence of a signal, an observed (expected) upper limit on the branching ratio of
BR(t -> eμq) < 1.6 (1.7) * 10^{-7} is set at the 95 % confidence level. An EFT interpretation is also discussed.
During Run 3 of LHC,
the elevated luminosity and pileup conditions call for advanced electronic systems to efficiently
trigger the physics objects.
Among the new processing units,
of high importance are the Feature Extractor (FEX) modules, responsible for identifying leptons and jets.
For the commissioning of these modules,
the design, testing and commissioning of a separate module, the FEX Test Module was needed.
In this thesis, the process of testing and commissioning this FPGA-based digital system is discussed.
Tests concerning the interpretation of incoming electrical signals as localised energy deposits in the ATLAS detector
by the electron FEX module firmware are also discussed briefly
Μελέτη του μειώσιμου υποβάθρου για τη διαδικασία H->4l με πραγματικά δεδομένα στον ανιχνευτή ATLAS
Get PDFΣκοπός της παρούσης εργασίας είναι η εκτίμηση του μειώσιμου υποβάθρου για τη διαδικασία Η→4l με μέθοδο οδηγούμενη από πραγματικά δεδομένα τα οποία έχουν συλλεχθεί κατά τα έτη 2015, 2016 σε ενέργειες κέντρου μάζας 13 TeV από τον ανιχνευτή ATLAS και αντιστοιχούν σε ολοκληρωμένη φωτεινότητα 36.1 fb-1. Το μειώσιμο υπόβαθρο, το οποίο εκτιμάται με την μεθοδολογία αυτή, αποτελείται από γεγονότα που περιλαμβάνουν την παραγωγή ενός μποζονίου Ζ σε συνδυασμό με αδρονικούς πίδακες (βαρέων και ελαφρών κουάρκ) καθώς και την παραγωγή γεγονότων ζεύγους κουάρκ top-antitop. Η μέθοδος που ακολουθείται στοχεύει στην εκτίμηση του υποβάθρου από γεγονότα 2l2μ (δηλ. με δευτερεύον ζεύγος λεπτονίων που απαρτίζεται από μιόνια) οπότε κυριαρχεί η συνεισφορά μιονίων που προέρχονται από διασπάσεις βαρέων κουάρκ. Παρά ταύτα, η ίδια μέθοδος εφαρμόζεται στην εργασία αυτή και για την περίπτωση δευτερεύοντος ζεύγους ηλεκτρονίων, και σχολιάζονται τα αποτελέσματα. Η μεθοδολογία βασίζεται στην ταυτόχρονη προσαρμογή με τη μέθοδο μεγίστης πιθανοφάνειας σε τέσσερις περιοχές ελέγχου, οι οποίες είναι ορθογώνιες μεταξύ τους καθώς και με την περιοχή που ικανοποιεί τα κριτήρια επιλογής γεγονότων για το σήμα. Οι φυσικές ποσότητες που χρησιμοποιούνται για τον ορισμό των περιοχών ελέγχου είναι η παράμετρος κρούσης των λεπτονίων ως προς την πρωτεύουσα κορυφή, η απομόνωση τους από τα λοιπά σωματίδια του γεγονότος και η ανισορροπία στη μέτρηση της ορμής των μιονίων μεταξύ εσωτερικού ανιχνευτή και φασματομέτρου μιονίων. Η προσαρμοζόμενη ποσότητα είναι η αναλλοίωτη μάζα του πρωτεύοντος ζεύγους λεπτονίων η οποία περιγράφεται με διαφορετική συνάρτηση πυκνότητας πιθανότητας για τα διαφορετικά υπό μελέτη υπόβαθρα. Όλες οι συστηματικές αβεβαιότητες υπεισέρχονται ως δεσμοί κατά τη διαδικασία προσαρμογής. Στην παρούσα εργασία, εκτός από τη μέτρηση του υποβάθρου μελετήθηκε η ευστάθεια της μεθοδολογίας ως προς το κριτήριο παραμέτρου κρούσης και ως προς το κριτήριο ανισορροπίας της μετρούμενης ορμής των μιονίων (που είναι εντονότερη για μιόνια προερχόμενα από διασπάσεις π/Κ εν πτήσει). Τέλος, παρουσιάστηκε η διαδικασία για την παραγωγή διαφορικών κατανομών με βάση την εκτίμηση του υποβάθρου από τα πραγματικά δεδομένα με παράδειγμα την αναλλοίωτη μάζα των 4 λεπτονίων.This thesis aims to study a method for the data-driven estimation of the reducible background for the process Η->4l. Data collected by the ATLAS detector, through the years 2015 and 2016 from pp collisions at center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 36.1 fb-1 are used. The sources of reducible background are the production of a Z boson in association with jets (both heavy flavor and light flavor) and the production of a tt ̅ pair. The composition of the reducible background depends on the flavor of the subleading lepton pair. The method followed in this thesis is primarily suited for 2l2μ events (i.e. with a subleading muon pair) where the main contribution stems from semileptonic decays of heavy hadrons. Nevertheless, it was also used for the first time in the estimation of 2l2e background and the first results are discussed. The method uses the simultaneous unbinned maximum likelihood fit in four control regions that are orthogonal to each other as well as to the signal region (the events that pass all the event selection criteria). The quantities that are used in the definition of the control regions include the lepton impact parameter w.r.t the primary vertex, the lepton isolation w.r.t the rest of the particles in the event and the muon transverse momentum imbalance measurement between the inner detector and the muon spectrometer. The fitted variable is the invariant mass of the leading lepton pair, which is described by different probability density functions to account for the different background components. All the systematic uncertainties are included as constraints in the final fit. In this thesis, apart from the background estimation, the stability of the method is studied w.r.t the lepton impact parameter and the momentum imbalance parameter (which exhibits stronger behavior in the case of π/Κ in flight decays). Finally, a procedure is presented for the construction of several differential distributions using the data driven background estimation and the invariant mass of the four leptons is given as an example
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
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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