1,721,091 research outputs found
Lattice QCD confronts the unitarity triangle fit.
No full textBefore the starting of the B factories, the Unitarity Triangle (UT) analysis relied on the results of lattice QCD simulations to relate the experimental determinations of semileptonic B decays, K0 - over(K, -)0 and Bd, s 0 - over(B, -)d, s 0 mixing to the CKM parameters. In the last years, much more information has been obtained from the direct determination of the UT angles from non-leptonic B decays. In this talk, we compare the results of the "classical" UT analysis (UTlattice) with the analysis based on the angles determinations (UTangles). We show that the recent measurement of Δ ms, combined with Δ md and εK, allows from this comparison a quite accurate extraction of the values of the lattice parameters, over(B, ̂)K, fB s over(B, ̂)B s 1 / 2, ξ and fB. These values, obtained "experimentally" by assuming the validity of the Standard Model, can be compared with the theoretical predictions from lattice QCD. We also discuss the different determinations of Vu b and show that current data do not favor the value measured in inclusive decays. Finally, we present updated predictions for the leptonic branching fraction B R (B → τ ντ), and compare them with the recent experimental determination. We take the opportunity of this write up to update the results of ref. [M. Bona et al. [UTfit Collaboration], arXiv:hep-ph/0606167] with the most recent results presented at the ICHEP'06 conference. © 2006 Elsevier B.V. All rights reserved
Production of neutral pseudo-Goldstone bosons at LEP II and NLC in multiscale walking technicolor models
No full textWalking technicolor (WTC) models predict the existence of heavy neutral pseudo-Goldstone bosons (PGBs), whose masses are typically expected to be larger than 100 GeV. In this paper, we investigate the production and decay of these particles at the high energy e(+)e(-) experiments, LEP II and NLC. We find that, in WTC models, the production of neutral PGBs can be significantly enhanced, by one or two orders of magnitude, with respect to the predictions of traditional (QCD-like) TC models. The origin of such an enhancement is the existence of several low energy TC scales, that are likely to appear in WTC theories. This could allow the PGBs to be observed even at the energy and luminosity of the LEP II experiment. At LEP II, the PGBs are expected to be produced in the e(+)e(-) --> P gamma channel, and, possibly, in the e(+)e(-) --> Pe(+)e(-) channel, with a total rate that can be of the order of several tenths per year. Due to the typical large values of PGB masses, the relative branching ratios of PGB decays, in WTC theories, are different from those predicted in traditional TC models. In particular, a large fraction of these decays can occur in the P --> gamma gamma channel. In considering the PGB production, at LEP II, we find that, in most of the final states, the distinctive signatures of WTC events should allow the Standard Model background to be reduced to a negligible level. We also find that, at a 500 GeV NLC experiment, the production of neutral PGBs can occur in several channels, and can be of the order of 10(3) events per year. Instead, when we consider traditional TC models, we find that no PGB are typically predicted to be observed, both at LEP II and the NLC experiment
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
Combined analysis of the unitarity triangle and CP violation in the Standard Model
No full textWe perform a combined analysis of the unitarity triangle and of the CP-violating parameter epsilon'/epsilon using tho most recent determination of the relevant experimental data and, whenever possible, hadronic matrix elements from lattice QCD. We discuss the role of the main non-per turbative parameters and make a comparison with other recent analyses. We use lattice results for the matrix clement of Q(8) obtained without reference to the strange quark mass. Since a reliable lattice determination or the matrix element of Q(6) is still missing, the theoretical predictions for epsilon'/epsilon suffer from large uncertainties. By evaluating this matrix clement with the vacuum-saturation approximation, we typically find as central value epsilon'/epsilon = (4-7) X 10(-4). We conclude that the experimental data suggest large deviation of the value of the matrix element of Q(6) from the vacuum-saturation approximation, possibly due to penguin contractions. (C) 2000 Elsevier Science B.V. All rights reserved
B0 - ANTI-B0 MIXING AND DECAY CONSTANTS WITH THE NONPERTURBATIVELY IMPROVED ACTION (41 cits. su spires)
No full textDispelling 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
- …
