1,721,015 research outputs found
Search for the Higgs boson decaying to bottom quarks and W boson tagging techniques at the ATLAS experiment at the LHC
Get PDFThe Standard Model of particle physics is currently the most complete theory of
subatomic particles. The discovery of the Higgs boson with a mass of 125 GeV
in 2012 further validated the Standard Model, providing evidence for the theory
that vector bosons obtain non-zero masses through the Higgs mechanism. Studies
are ongoing to determine the exact nature and properties of the Higgs boson. A
Higgs boson of this mass is predicted to decay to a pair of b-b quarks with a
branching ratio of 58%, however this decay mode has not yet been observed.
This thesis presents a search for the associated production of a Higgs boson with
a leptonically decaying W boson, WH → ℓvb-b, using 20.3 fb-1 of Run 1 data
collected by ATLAS at the LHC from pp collisions at a centre-of-mass energy
of ps = 8 TeV. The observed (expected) significance of a Higgs boson with a
mass of 125 GeV for the WH → ℓvb-b process is found to be 2:7σ (1:3σ). The
measured cross section in units of the expected Standard Model cross section has
a best-fit value of μ = μ/μSM = 2:2+0:67-0:64(stat:)+0:7-0:59(syst:) = 2:2+0:97-0:87. The results
are combined with the search for ZH → v-vb-b and ZH → ℓ+ℓ-b-b to provide a
best-fit value of μ = μ/μSM = 1:1+0:61-0:56. The start of Run 2 of the LHC in 2015 saw the collision energy being raised
to √s = 13 TeV, increasing the probability of particles being produced with
a large momentum boost. At these high energies there is also a possibility to
discover new particles and interactions. An extension of the Standard Model, the
Heavy Vector Triplet (HVT) model, describes new heavy vector bosons W¹ and
Z¹, which can decay to pairs of heavy bosons (W, Z or Higgs bosons). If the
W0 and Z0 bosons are sufficiently heavy, the hadronic decays of the diboson final
states produce boosted jets. In this thesis, methods for identifying hadronically
decaying boosted bosons are developed, based on techniques that examine the
internal substructure of the jet. Multiple substructure variables are combined into a single discriminant using two
machine learning techniques: boosted decision trees and deep neural networks.
Simulated events of W¹→WZ → q-qq-q are used to develop these boosted W boson
taggers. An improvement in the background rejection power, whilst keeping 50% of the signal, over previous boosted W boson taggers of up to 13%-when using
deep neural networks-and 36%-when using boosted decision trees-is obtained.
The performance of the new boosted W boson taggers are evaluated in a search
for a narrow WW resonances from the decay of a Z¹ with boson-tagged jets in
3.2 fb-1 of pp collisions at √s = 13 TeV collected with the ATLAS detector
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
A study of the charmless decays of charged β mesons to the final states #KAPPA##+-##pi##-+##pi##+-# using the BABAR detector
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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
Computing in High Energy and Nuclear Physics (CHEP) 2012
No full textWe describe recent I/O testing frameworks that we have developed and applied within the UK GridPP Collaboration, the ATLAS experiment and the DPM team, for a variety of distinct purposes. These include benchmarking vendor supplied storage products, discovering scaling limits of SRM solutions, tuning of storage systems for experiment data analysis, evaluating file access protocols, and exploring IO read patterns of experiment software and their underlying event data models. With multiple grid sites now dealing with petabytes of data, such studies are becoming increasingly essential. We describe how the tests build, and improve, on previous work and contrast how the use-cases differ. We also detail the results obtained and the implications for storage hardware, middleware and experiment software
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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