1,720,954 research outputs found
Search for pair production of heavy particles decaying to a top quark and a gluon and development of ML-based L1 trigger strategies at the CMS experiment
Get PDFIn this thesis, I present a search for a potential signature of new physics: the existence of a new resonance t*, characterized by its decay into a top quark and a gluon. I use 138 fb^{-1} of proton-proton collision events gathered with the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). I analyze events with a single lepton, multiple jets, and missing transverse momentum and enrich potential signal events using a deep neural network (DNN). I utilize an an active, two-step decorrelation procedure to ensure that the DNN is independent of the sensitive variable ST of the search. This variable is defined as a scalar energy sum of all considered objects. I analyze distributions of ST in search for pair production of t* with either spin-1/2 or spin-3/2. The results agree with Standard Model predictions. Therefore, I set exclusion limits on the production cross section of t*. In the spin-1/2 case, these are between 120 fb for m_{t*} = 700 GeV and 0.8 fb for m_{t*} = 3000 GeV. For t* with spin-3/2 , the exclusion limits are between 15 fb for m_{t*} = 700 GeV and 1.0 fb for m_{t*} = 2750 GeV. Assuming all t* decay as t -> tg, I exclude the existence of t* below a mass of 1050 GeV for spin-1/2 and 1700 GeV for spin-3/2. These are the most stringent exclusion limits for this particle to date. In a second part, I present the development of algorithms for the Level-1 trigger (L1T) of CMS, which utilize machine learning to improve on currently used algorithms. Due to the high collision rate in CMS and the resulting immense data streams, the L1T needs to decide whether to store or discard an event at a rate of 40 MHz. Especially towards the high-luminosity phase of the LHC, novel techniques will be crucial for CMS to ensure optimal performance of the trigger system. I present studies on the optimization, hardware integration and usage of a trigger based on a neural network. I show that events of a HH -> bbWW (single muon) process can be selected more effectively than with classical algorithms using a lightweight neural network. I demonstrate that this network can be integrated into the hardware of the CMS L1T.In dieser Arbeit präsentiere ich eine Suche nach einer potentiellen Signatur neuer Physik: der Existenz einer Resonanz t*, die in ein Top-Quark und ein Gluon zerfällt. Ich verwende 138 fb^{-1} an Daten von Proton-Proton Kollisionen, die mit dem Compact Muon Solenoid (CMS) Detektor am Large Hadron Collider (LHC) gemessen wurden. Ich analysiere Ereignisse mit einem Lepton, Jets und fehlendem transversalen Impuls und reichere potentielle Signal-Ereignisse mithilfe eines Deep Neural Networks (DNN) an. Ich nutze eine aktive, zweistufige Dekorrelationsprozedur um sicherzustellen, dass das DNN unabhängig von der sensitiven Variable ST der Suche ist. Diese ist als skalare Impulssumme aller betrachteten Objekte definiert. Ich analysiere ST-Verteilungen auf der Suche nach Paarproduktion von t* mit Spin-1/2 oder Spin-3/2. Meine Resultate stimmen mit den Vorhersagen des Standardmodelles überein, so kann ich die Paarproduktion von t* mit Spin-1/2 , je nach Masse des t*, für Wirkungsquerschnitte zwischen 120 fb für m_{t*} = 700 GeV und 0.8 fb für m_{t*} = 3000 GeV ausschließen. Für ein t* mit Spin-3/2 liegen die Ausschlussgrenzen zwischen 15 fb für m_{t*} = 700 GeV und 1.0 fb für m_{t*} = 2750 GeV. Unter der Annahme, dass alle t* als t* -> tg zerfallen, kann die Existenz eines t* unterhalb einer Masse von 1050 GeV für Spin-1/2 bzw. 1700 GeV für Spin-3/2 ausgeschlossen werden. Dies sind die bisher stringentesten Ausschlussgrenzen für dieses Teilchen. In einem zweiten Teil präsentiere ich die Entwicklung von Algorithmen für den Level-1 Trigger (L1T) von CMS, die mithilfe von maschinellem Lernen versuchen
eine Verbesserung gegenüber aktuellen Algorithmen zu erzielen. Aufgrund der hohen Kollisionsrate in CMS und den daraus resultierenden immensen Datenströmen muss der L1T mit einer Rate von 40 MHz entscheiden, ob ein Ereignis gespeichert wird. Insbesondere in Hinblick auf die zukünftige ”High-Luminosity”-Phase des LHC sind solche neuartigen Techniken unabdingbar für CMS, um die Effektivität des Triggersystems zu gewährleisten. Ich führe Studien zur Optimierung, Hardwareintegration und Nutzung eines Triggers, der auf einem Neuronalen Netz basiert durch. Ich zeige, dass Ereignisse des Prozesses HH -> bbWW, die ein einzelnes Muon enthalten, mithilfe eines kleinen neuronalen Netzwerkes effektiver selektiert werden können als mit klassischen Algorithmen. Ich demonstriere, dass dieses Netzwerk in die Hardware des L1T von CMS integriert werden kann
Searches for new resonances coupling to third generation quarks at CMS
No full textAn overview of recent searches for new physics with top and bottom quarks in the final state is presented, using proton-proton collision data collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV. The presented analyses search for partners of standard model particles an excited bottom quark , new massive boson or top quark partner . Jet tagging techniques are used to reconstruct and identify jets originating from highly boosted objects in order to improve sensitivity. No significant deviation from standard model predictions are observed, therefore stringent exclusion limits on the production cross sections of all analyzed particles are set. A range of different particle masses and chirality hypotheses are considered
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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