1,721,047 research outputs found
Topics in Particle Physics
No full text這篇論文由四個部分組成。在第一個部分，我們提供一個粒子物理學的介紹。我們將介紹粒子物理學的標準模型以及超越標準模型的理論，亦會介紹大型強子對撞機(LHC)以及超環面儀器(ATLAS)這兩個粒子物理學的領先實驗儀器。在第二個部分，我們研究一個於2014年被提出的理論模型。在這個模型當中，光在一重力位中的速度會因量子力學的修正而改變。我們展示這個理論所預測的修正與廣義相對論的精密度測試互相衝突。我們提出一個對該模型的修改，並討論它的含義。在第三個部分，我們描述一個利用超環面儀器來搜索於√s=13 TeV質子質子碰撞實驗中產生渺子濤子最終態的超越標準模型的現象的實驗過程及結果。在第四個部分，我們描述一個供超環面儀器用的可見濤子能量校準的開發工作。這個新的校準建基於多重變量分析及機器學習算法。The thesis consists of four parts. In part I, an introduction to particle physics is given. We introduce the Standard Model of particle physics and theories that lie beyond the Standard Model. The LHC and the ATLAS detector, which are apparatus of leading experiments in particle physics, are also introduced. In part II, we study a theoretical model proposed recently in 2014 in which the speed of light in a gravitational potential is altered by quantum mechanical corrections. We show that the predicted correction is in conflict with precision tests of general relativity. A modification to the original model is proposed, and we discuss its implications. In part III, we describe the process and results of a search for phenomena beyond the Standard Model in the µt final state in p-p collisions at vs = 13 TeV with the ATLAS detector. In part IV, we describe the development work for a new visible tau energy calibration for the ATLAS detector based on multivariate analysis and machine learning algorithms.Chan, Wing Sheung.Thesis M.Phil. Chinese University of Hong Kong 2016.Includes bibliographical references (leaves ).Abstracts also in Chinese.Title from PDF title page (viewed on …).Detailed summary in vernacular field only
Limit on Branching Fraction
No full textA search for the decay Bs -> mu+mu- has been performed using proton-proton collisions recorded with the ATLAS detector at the LHC. The Standard Model predicts the time-integrated branching fraction for the decay to be extremely small. CLs tests method is used in extracting upper limit of the branching fraction from the experimental data. This report describes the two test methods used, the counting method and the mass fit method, and compares them
Search for lepton-flavour-violating decays of the boson into a -lepton and a light lepton with the ATLAS detector
No full textLepton flavour violation in the charged lepton sector is an unambiguous signal of physics beyond the Standard Model. Searches for lepton flavour violation in decays of the boson with the ATLAS detector is reported, focusing on decays into an electron or muon and a hadronically decaying -lepton, using collisions data with a centre-of-mass energy of 13 TeV. Upper limits on the branching ratios of lepton-flavor-violating decays are set at the 95 % confidence level: and . When combined with a previous ATLAS result based on collisions data with a centre-of-mass energy of 8 TeV, an upper limit of is obtained
Search for lepton-flavor-violating decays of the boson into a -lepton and a light lepton with the ATLAS detector
No full textLepton flavour violation in the charged lepton sector is an unambiguous signal of physics beyond the Standard Model. Searches for lepton flavour violation in decays of the boson with the ATLAS detector is reported, focusing on decays into an electron or muon and a hadronically decaying -lepton, using collisions data with a centre-of-mass energy of 13 TeV. Upper limits on the branching ratios of lepton-flavor-violating decays are set at the 95% confidence level: and . When combined with a previous ATLAS result based on collisions data with a centre-of-mass energy of 8 TeV, an upper limit of is obtained
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
No full textWe 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
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