1,721,062 research outputs found
Electron heating in subpicosecond laser interaction with overdense and near-critical plasmas
Get PDFn this work we investigate electron heating induced by intense laser interaction with micrometric flat solid
foils in the context of laser-driven ion acceleration. We propose a simple law to predict the electron temperature in
a wider range of laser parameters with respect to commonly used existing models. An extensive two-dimensional
(2D) and 3D numerical campaign shows that electron heating is due to the combined actions of j×B
and Brunel effect. Electron temperature can be well described with a simple function of pulse intensity and angle of incidence,
with parameters dependent on pulse polarization. We then combine our model for the electron temperature with
an existing model for laser-ion acceleration, using recent experimental results as a benchmark. We also discuss
an exploratory attempt to model electron temperature for multilayered foam-attached targets, which have been
proven recently to be an attractive target concept for laser-driven ion acceleration
Discovery and mass spectroscopy via mixed Di-Boson production at the LHC in a 4-Site model with a composite Higgs Boson
No full textWe investigate the scope of the Large Hadron Collider (LHC) in probing the parameter space of a 4-Site (4S) model supplemented by one composite Higgs state. We concentrate on the yield of 'mixed' di-boson production giving three leptons and missing (transverse) energy in the final state, i.e., events induced via the sub-process q\bar q' -> l^+\nu_l l^{'+}l^{'-} + , where are quarks and in all possible combinations, signature which enables the production in the intermediate steps of all additional -- with respect to the Standard Model (SM) -- neutral and charged gauge bosons belonging to the spectrum of this scenario, all of which in resonant topologies. We not only find this channel to be accessible over the background but also show that, after a dedicated cut-based analysis, kinematical reconstruction of all such resonances is always possible. We finally compare the yield of the mixed di-boson mode to that of the 'charged' di-boson one and find that the former is of lesser scope than the latter at smaller gauge boson masses but it overcomes it at higher values, thereby revealing itself a viable search mode covering new regions of parameter space
Particle acceleration and radiation friction effects in the filamentation instability of pair plasmas
No full textThe evolution of the filamentation instability produced by two counterstreaming, ultrarelativistic pair plasmas is studied with particle-in-cell simulations. Radiation friction effects are taken into account. Two-dimensional simulations are performed for both cases of the initial momenta being perpendicular (T mode) or parallel (P mode) to the simulation plane. In the initial stage, the instability is purely transverse for both modes and generates small-scale filaments which later merge into larger structures. Particle acceleration leads to a strong broadening of the energy spectrum with the formation of a peak at twice the initial energy for the T mode. In the non-linear stage, significant differences between T- and P modes in the evolution of the fields and in the spectra of accelerated particles are apparent. The presence of radiative losses does not change the dynamics of the instability but strongly affects the structure of the particle spectra in the ultrarelativistic regime (particle energy > 100 MeV) and for high plasma densities (> 10(21) cm(-3))
Drell-Yan production at the LHC in a four site Higgsless model
No full textWe consider a four site Higgsless model based on the SU(2)L × SU(2)1 × SU(2)2 × U(1)Y gauge symmetry, which predicts two neutral and four charged extra gauge bosons, Z1,2 and W±1,2. We compute the properties of the new particles, and derive indirect and direct limits on their masses and couplings from LEP and Tevatron data. In contrast to other Higgsless models, characterized by fermiophobic extra gauge bosons, here sizeable fermion-boson couplings are allowed by the electroweak precision data. The prospects of detecting the new predicted particles in the favoured Drell-Yan channel at the LHC are thus investigated. The outcome is that all six extra gauge bosons could be discovered in the early stage of the LHC low-luminosity run
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
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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