1,721,049 research outputs found
Measurement of the t distribution in diffractive photoproduction at HERA.
No full textPhoton diffractive dissociation, gamma p --> Xp, has been studied at HERA with the ZEUS detector using ep interactions where the virtuality Q^2 of the exchanged photon is smaller than 0.02 GeV^2. The squared four-momentum t exchanged at the proton vertex was determined in the range 0.073 < \t\ < 0.40 GeV^2 by measuring the scattered proton in the ZEUS Leading Proton Spectrometer. In the photon-proton centre-of-mass energy interval 176 < W < 225 GeV and for masses of the dissociated photon system 4 < M(x) < 32 GeV, the t distribution has an exponential shape, dN/d\t\ proportional to exp (-b\t\), with a slope parameter b = 6.8 +/- 0.9 (stat.)(-1.1)(+1.2) (syst.) GeV^(-2)
Measurement of the diffractive structure function F_2(D4) at HERA
No full textThis paper presents the first analysis of diffractive photon dissociation events in deep inelastic positron-proton scattering at HERA in which the proton in the final state is detected and its momentum measured. The events are selected by requiring a scattered proton in the ZEUS leading proton spectrometer (LPS) with x_L > 0.97, where x_L is the fraction of the incoming proton beam momentum carried by the scattered proton. The use of the LPS signicantly reduces the contamination from events with diffractive dissociation of the proton into low mass states and allows a direct measurement of t, the square of the four-momentum exchanged at the proton vertex
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
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