1,721,069 research outputs found
Virtual QCD corrections to gg → ZZ: top-quark loops from a transverse-momentum expansion
No full textWe present the virtual corrections due to the top-quark loops for the process gg → ZZ at next-to-leading order in QCD. The associated two-loop box diagrams are computed using a small-transverse-momentum expansion. Our results are then merged with those available in the complementary energy region, obtained via a high-energy expansion, in order to provide an analytic result that is valid in the whole phase space. The results presented allow for an efficient modelling of the signal-background interference as well as the irreducible background in off-shell Higgs production
The effect of an anomalous Higgs trilinear self-coupling on the
No full textWe compute the two-loop effects induced by an anomalous Higgs trilinear self-coupling in the partial decay width . The computation is performed using the anomalous coupling approach, working in the unitary gauge, and in a theory in which the anomalous coupling is generated via the addition to the scalar potential part of the Standard Model Lagrangian of an (in)finite tower of terms. The former computation is automatically finite while the latter requires the renormalization of the lowest order contribution. We discuss the renormalization conditions that should be employed in order to obtain the same result in the two approaches. We find that the process is one of the most sensitive mode to an anomalous trilinear Higgs self-coupling. As a by-product of this work we confirm one of two different results present in the literature concerning the contribution of an anomalous Higgs trilinear coupling in the decay
Purification and characterization of ferulate and p-coumarate decarboxylase from Bacillus pumilus
No full textBacillus pumilus PS213 isolated from bovine ruminal fluid was able to transform ferulic acid and p-coumaric acid to 4-vinylguaiacol and 4-vinylphenol, respectively, by nonoxidative decarboxylation. The enzyme responsible for this activity has been purified and characterized. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of crude extract from a culture induced by ferulic acid or p-coumaric acid shows three bands that are not present in the crude extract of an uninduced culture, while the purified enzyme shows a single band of 23 kDa; the molecular mass calculated by size exclusion chromatography is 45 kDa. Enzyme activity is optimal at 37 degrees C and pH 5.5 and is not enhanced by any cation. Kinetic studies indicated a Km of 1.03 mM and a Vmax of 0.19 mmol.min-1/mg.liter-1 for ferulic acid and a Km of 1.38 mM and a Vmax of 0.22 mmol.min-1/mg.liter-1 for p-coumaric aci
On the NLO QCD corrections to gluon-initiated ZH production
No full textWe compute the QCD corrections at next-to-leading order for the process gg → ZH, including both the virtual two-loop terms and real-emission contributions. The two-loop box diagrams in the virtual corrections are approximated analytically over the complete phase space, combining the results of an expansion in the limit of small transverse momentum and an expansion in the regime of high energy. We obtain both inclusive and differential results for the cross section. We find that the NLO QCD corrections are of the same size as the LO contribution up to ZH invariant masses close to 1 TeV, but they
increase significantly when higher energies are considered, due to a class of real-emission diagrams in which the Z boson is radiated from an open quark line. Finally, we estimate the uncertainty due to the renormalization scheme used for the top-quark mass both on
the total and differential cross section
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
On the neutral Higgs boson masses in the MSSM for arbitrary stop mixing
No full textWe compute the O(alpha_t alpha_s) two-loop corrections to the neutral Higgs boson masses in the Minimal Supersymmetric extension of the Standard Model. An appropriate use of the effective potential allows us to obtain simple analytical formulae, valid for arbitrary values of mA and of the mass parameters in the stop sector. We elucidate some subtleties of the effective potential calculation, and find full agreement with the numerical output of the existing diagrammatic calculation. We discuss in detail the limit of heavy gluino
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
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