1,721,943 research outputs found
Scaling in gamma*p total cross-sections, saturation and the gluon density
No full textSchildknecht D, Surrow B, Tentyukov M. Scaling in gamma*p total cross-sections, saturation and the gluon density. MODERN PHYSICS LETTERS A. 2001;16(28):1829-1839.Including the new HERA data, the gamma *p total cross-section is analyzed in the generalized vector dominance/color-dipole picture (GVD/CDP) that contains scaling in eta = (Q(2) + m(0)(2))/Lambda (2)(W-2), where Lambda (2)(W-2) is an increasing function of W-2. At any Q(2), for W-2 --> infinity, the cross-sections for virtual and real photons become identical, sigma (gamma *p)(W-2, Q(2))/(sigma gammap)(W-2) --> 1. The gluon density deduced from the color-dipole cross-section fulfills the leading order DGLAP relationship. Evolution a la DGLAP breaks down for n less than or similar to 0.1
Diffraction and sigma(gamma*rho)
No full textSchildknecht D, Tentyukov M, Kuroda M, Surrow B. Diffraction and sigma(gamma*rho). ACTA PHYSICA POLONICA B. 2002;33(11):3431-3438.The empirical scaling law, wherein the total photo-absorption cross section depends on the single variable eta = (Q(2) + m(0)(2))/A(2)(W-2), provides em pirical evidence for saturation in the sense of sigma(gamma*p)(W-2, Q(2))/sigma(gammap)(W-2) --> 1 for W-2 --> infinity at fixed Q(2). The total photo-absorption cross section is related to elastic diffraction in terms of a sum rule. The excess of diffractive production over the elastic component is due to inelastic diffraction that contains the production of hadronic states of higher spins. Motivated by the diffractive mass spectrum, the Generalized Vector Dominance/Color Dipole Picture (GVD/CDP) is extended to successfully describe the DIS data in the full region of x 0, where the diffractive two-gluon exchange mechanism dominates
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
Low-x scaling in gamma*p total cross sections
No full textSchildknecht D, Surrow B, Tentyukov M. Low-x scaling in gamma*p total cross sections. PHYSICS LETTERS B. 2001;499(1-2):116-124.We show that the experimental data for the total virtual-photon proton cross section, sigma gamma *p(W-2,Q(2)) for x(bj) less than or similar to 0.1 lie on a universal curve, when plotted against eta = (Q(2) + m(0)(2))/Lambda (2)(W-2), where Lambda (2)(W-2) = C-l(W-2 + W-0(2))(C2) is determined by the parameters C-1, C-2 and W-0(2) . The observed scaling law follows from the generalized-vector-dominance/colour-dipole picture (GVD/CDP) of low-x deep inelastic scattering. (C) 2001 Elsevier Science B.V. All rights reserved
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
Vector-meson electroproduction from generalized vector dominance
No full textSchildknecht D, Schuler GA, Surrow B. Vector-meson electroproduction from generalized vector dominance. PHYSICS LETTERS B. 1999;449(3-4):328-338.Including destructively interfering off-diagonal transitions of diffraction-dissociation type, we arl ive at a formulation of GVD for exclusive vector-meson production in terms of a continuous spectral representation of dipole form. The transverse cross-section, sigma(T.gamma*p) (-->) (Vp), behaves asymptotically as 1/Q(4), while R-v equivalent to sigma(L.gamma*p --> Vp)/sigma(T.gamma*p --> Vp) becomes asymptotically constant. Contributions violating s-channel helicity conservation stay at the level established in low-energy photoproduction and diffractive hadron-hadron interactions. The data on rho(0)-meson production from the Fermilab E665 Collaboration and on phi- and rho(0)-meson production from HERA are found to be in agreement with these predictions. (C) 1999 Elsevier Science B.V. All rights reserved
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