1,720,969 research outputs found
Distribution amplitudes of light-quark mesons from lattice QCD
Full text linkAbstract not availableJorge Segovia, Lei Chang, Ian C. Cloët, Craig D.Roberts, Sebastian M. Schmidt, Hong-shi Zon
Charge symmetry breaking effects in pion and kaon structure
No full textPublished 17 May 2018Charge symmetry breaking (CSB) effects associated with the u and d quark mass difference are investigated in the quark distribution functions and spacelike electromagnetic form factors of the pion and kaon. We use a confining version of the Nambu–Jona-Lasinio model, where CSB effects at the infrared scale associated with the model are driven by the dressed u and d quark mass ratio, which because of dynamical chiral symmetry breaking is much closer to unity than the associated current quark mass ratio. The pion and kaon are given as bound states of a dressed quark and a dressed antiquark governed by the Bethe-Salpeter equation, and exhibit the properties of Goldstone bosons, with a pion mass difference given by m2 π + − m2 π0 ∝ (mu − md )² as demanded by dynamical chiral symmetry breaking.We find significant CSB effects for realistic current quark mass ratios (mu/md ∼ 0.5) in the quark flavor-sector electromagnetic form factors of both the pion and kaon. For example, the difference between the u and d quark contributions to the π + electromagnetic form factors is about 8% at a momentum transfer of Q² ≃ 10 GeV², while the analogous effect for the light quark sector form factors in the K⁺ and K⁰ is about twice as large. For the parton distribution functions we find CSB effects which are considerably smaller than those found in the electromagnetic form factors.Parada T. P. Hutauruk, Wolfgang Bentz, Ian C. Cloët, and Anthony W. Thoma
Reduction of Protein Networks Models by Passivity Preserving Projection
Full text linkWe survey contemporary studies of hadrons and strongly interacting quarks using QCD’s Dyson–Schwinger equations, addressing the following aspects: confinement and dynamical chiral symmetry breaking; the hadron spectrum; hadron elastic and transition form factors, from small- to large-Q²; parton distribution functions; the physics of hadrons containing one or more heavy quarks; and properties of the quark gluon plasma.Adnan Bashir, Chang Lei, Ian C. Cloët, Bruno El-Bennich, Liu Yu-Xin, Craig D. Roberts and Peter C. Tand
Quark distributions in nucleons and nuclei
Full text linkParallel Session B Light QuarksWe discuss the medium modifications of quark distributions and structure functions in the framework of a chiral effective quark theory. Particular emphasis is put on the isospin dependence of the in-medium quark distributions. As an interesting application, we discuss a possible solution of the so called NuTeV anomaly. Possible extensions of the model to describe fragmentation functions are also discussed.Wolfgang Bentz, Ian C. Cloët, Takuya Ito, Anthony W. Thomas, K. Yazak
SU(3)-flavor breaking in octet baryon masses and axial couplings
No full textPublished 23 December 2014The lightest baryon octet is studied within a covariant and confining Nambu–Jona-Lasinio model. By solving the Poincaré covariant Faddeev equations—including scalar and axialvector diquarks—we determine the baryon octet masses and axial charges for strangeness conserving transitions. For the axial charges the degree of violation of SU(3) flavor symmetry, arising because of the strange spectator quark(s), is found to be no more than 10%.Manuel E. Carrillo-Serrano, Ian C. Cloët, and Anthony W. Thoma
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
Dihadron fragmentation functions from the NJL-jet model and their QCD evolution
Full text linkWe present results for dihadron fragmentation functions from the Nambu–Jona-Lasinio-jet model evolved from the model scale to a typical experimental scale of 4 GeV². The numerical method used in this evolution is discussed in detail. The effect of evolution on the shapes of the dihadron fragmentation functions is discussed for a doubly favored process (u→π⁺π⁻), as well as a singly favored (u→π⁺K⁻) process involving light quarks. Finally, we explore the production of K⁺K⁻ pairs from an initial u, d or s quark.Andrew Casey, Ian C. Cloët, Hrayr H. Matevosyan, and Anthony W. Thoma
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