1,721,017 research outputs found
Strange particle production in final states in collisions at TeV with the ATLAS detector at the LHC
No full textThe LHC has opened up a new era in particle physics in as much it paved the way for the discovery of the Higgs boson, the missing piece in the so called standard model (SM) , pushing the lower limits for particles predicted in many beyond the standard model (BSM) scenarios to values well above the TeV scale, allowing precision measurements at unprecedented energies. This ambitious scientific program has been carried out with the construction of two big multipurpose detectors: ATLAS and CMS. The discovery of the Higgs boson is, no doubt, one of the most important milestones in the history of particle physics. Another field where one can reach unprecedented precision is in the study of the top quark. With the advent of unprecedented statistics for top quark pair production, one can think of directly measuring the Cabibbo-Kobayashi-Maskawa matrix elements where the top quark is involved, in particular . Ali et al. [Phys. Lett. B 693 (2010) 44-51] made the proposal to determine this matrix element by discerning the signal final state from the dominant background process . This could be done by looking at neutral strange particle production which turns out to be leading in -quark jets while non-leading in -quark jets as -quarks decay sequentially . This proposal makes use of MVA techniques, with the possible existence of jet secondary vertices and soft leptons as additional variables with discriminant power. Therefore this proposal is dependent on the good agreement between data and Monte Carlo generators used in the training phase. However the proposal we refer to is qualitatively right, but quantitatively is somewhat overoptimistic as it is based on generator level data. The aim of the present thesis is twofold: on the one hand, as a continuation of the thesis presented in 2015 by Dr. Javier Llorente, who measured - and light-jet shapes in events, we have investigated the improvements in the performance of the MVA discussed above when adding the jet shapes as a discriminant variable. This was presented at ICHEP 2014 in Valencia, [Nucl. Part. Phys. Proc. 273-275 (2016) 2761-2763]. This is the basis for Chapter 4 in this thesis. On the other hand, we made use of the ATLAS data at 7 TeV taken in 2011, to study neutral strange particle production in the dileptonic final states. This study has been published in Eur. Phys. J. C 79 (2019) 1017. It is found that neutral strange particle production embedded in jets, -tagged or not, is well described by current MC models like the following generators: POWHEG+PYTHIA6, POWHEG+PYTHIA8, MC@NLO+HERWIG, POWHEG+HERWIG7, aMC@NLO+HERWIG7 or SHERPA. This lends support to the idea put forward by ABL that one could attempt to determine with a TMVA. Furthermore, neutral strange particles produced outside jets, the dominant contribution, in underestimated by current MC generators by 30 %. Thus, these data have the potential to help tune models for MPI. This is summarised in Chapter 5. For the sake of completeness and without any pretension to originality, the first three chapters are devoted to present the most relevant aspects of the SM, Chapter 1, the ATLAS detector and the LHC, Chapter 2, and the objects (leptons, jets, missing energy) reconstruction, Chapter 3
Measurements of and production in dileptonic events in collisions at with the ATLAS detector.
No full textMeasurements of and production in final states have been performed. They are based on a data sample with integrated luminosity of 4.6 from proton--proton collisions at a centre-of-mass energy of 7 TeV, collected in 2011 with the ATLAS detector at the Large Hadron Collider. Neutral strange particles are separated into three classes, depending on whether they are contained in a jet, with or without a -tag, or not associated with a selected jet. The aim is to look for differences in their main kinematic distributions. A comparison of data with several Monte Carlo simulations using different hadronisation and fragmentation schemes, colour reconnection models and different tunes for the underlying event has been made. The production of neutral strange particles in dileptonic events is found to be well described by current Monte Carlo models for and production within jets, but not for those produced outside jets
Fragmentation studies with the ATLAS detector
No full textGluon splitting to b-quark pairs is a unique probe into the properties of gluon fragmentation, as identified b-tagged jets provide a proxy for the quark daughters of the initial gluon. If available, we present a measurement of key differential distributions related to g→b bbar using data collected with the ATLAS detector at √s=13 TeV. Track jets are used to probe angular scales below the standard R=0.4 jet radius. The observables are unfolded to particle level in order to facilitate direct comparison with predictions from simulations and provide an important constraint to hadronization models. If available, a measurement of the properties of jet fragmentation performed with pp data collected with the ATLAS detector at √s=13 TeV is presented. Charged particle tracks are used to measure charged particle multiplicity, the jet charge, the summed fragmentation function, the momentum transverse to the jet axis, and the radial profile of the jet. Each observable is unfolded to correct for acceptance and detector effects. Exclusive interpretations in terms of quarks and gluons are provided in order to directly compare with state-of-the-art calculations
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
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