1,721,313 research outputs found
On the observation of bosonic loop corrections in electroweak precision experiments
No full textDittmaier S, Schildknecht D, Weiglein G. On the observation of bosonic loop corrections in electroweak precision experiments. NUCLEAR PHYSICS B. 1996;465(1-2):3-22.We investigate the structure of the experimentally significant electroweak bosonic loop corrections to the leptonic weak mixing angle, the leptonic Z-boson decay width, and the W-boson mass. It is shown that the bosonic corrections that have a sizable effect at the present level of experimental accuracy are directly related to the use of the Fermi constant G(mu) as input parameter for analyzing the LEP observables. Indeed, if the (theoretical value of the) leptonic width of the W boson is used as input parameter instead of the low-energy parameter G(mu) determined from muon decay, fermion-loop corrections are sufficient for compatibility between theory and experiment
Towards High-Precision Predictions for the MSSM Higgs Sector
Full text linkThe status of the evaluation of the MSSM Higgs sector is reviewed. The
phenomenological impact of recently obtained corrections is discussed. In
particular it is shown that the upper bound on m_h within the MSSM is shifted
upwards. Consequently, lower limits on tan beta obtained by confronting the
upper bound as function of tan beta with the lower bound on m_h from Higgs
searches are significantly weakened. Furthermore, the region in the M_A-tan
beta-plane where the coupling of the lightest Higgs boson to down-type fermions
is suppressed is modified. The presently not calculated higher-order
corrections to the Higgs-boson mass matrix are estimated to shift the mass of
the lightest Higgs boson by up to 3 GeV
Which bosonic loop corrections are tested in electroweak precision measurements?
No full textDittmaier S, Schildknecht D, Weiglein G. Which bosonic loop corrections are tested in electroweak precision measurements? ACTA PHYSICA POLONICA B. 1996;27(10):2507-2524.The nature of the electroweak bosonic loop corrections to which current precision experiments are sensitive is explored. The set of effective parameters Delta x, Delta y, and epsilon, which quantify SU(2) violation in an effective Lagrangian, is shown to be particularly useful for this purpose. The standard bosonic corrections are sizable only in the parameter Delta y, while Delta x and epsilon are sufficiently well approximated by the pure fermion-loop prediction. By analyzing the contributions to Delta y it is shown that the bosonic loop corrections resolved by the present precision data are induced by the change in energy scale between the low-energy process muon decay and the energy scale of the LEP1 observables. If the (theoretical value of the) leptonic width of the W boson is used as input parameter instead of the Fermi constant G(mu), no further bosonic loop corrections are necessary for compatibility between theory and experiment
How reliably can the Higgs-boson mass be predicted from electroweak precision data?
No full textDittmaier S, Schildknecht D, Weiglein G. How reliably can the Higgs-boson mass be predicted from electroweak precision data? PHYSICS LETTERS B. 1996;386(1-4):247-257.From the LEP precision data and the measurement of the W-boson mass, upon excluding the observables R(b), R(c) in a combined fit of the top-quark mass, m(t), and the Higgs-boson mass, M(H), within the Standard Model, we find the weak 1 sigma bound of M(H) less than or similar to 900 GeV. Stronger upper bounds on M(H), sometimes presented in the literature, rely heavily on the inclusion of R(b) in the data sample, Upon including R(b), the quality of the fit drastically decreases, and by carefully analyzing the dependence of the fit results on the set of experimental input data we conclude that these stronger bounds are not reliable. Moreover, the stronger bounds on M(H) are lost if the deviation between theory and experiment in R(b) is ascribed to contributions of new physics. Replacing s(W)(-2)(LEP) by the combined value s(W)(-2)(LEP+SLD) in the data sample leads to a bound of M(H) less than or similar to 430 GeV at the 1 sigma level. The value of S-W(-2)(SLD) taken alone, however, gives rise to fit results for M(H) which are in conflict with M(H) greater than or similar to 65.2 GeV from direct searches
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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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