1,721,089 research outputs found
Neutralino annihilation into a photon and a Z boson
No full textA full one-loop calculation of neutralino S-wave annihilation into the Z gamma final state is performed in the minimal supersymmetric extension of the standard model. This process, like the similar one with two photons in the final state, may be of importance for the indirect detection of supersymmetric dark matter through the very narrow gamma ray line that would result from neutralino annihilations in the galactic halo. We give the complete analytical formulas for this loop-induced process and treat the case of a pure Higgsino as a first application of our expressions. Predictions for the gamma line flux are given for the halo model which is of the form suggested by Kravtsov et al. and for the profile proposed by Navarro, Frenk and White, For heavy neutralinos, the lines from 2 gamma and Z gamma would have indistiguishable energy in a realistic detector, making the fluxes add and facilitating discovery. For lighter neutralinos, the positions and relative strengths of the two lines would give valuable information on the nature of the supersymmetric dark matter particles
Full one-loop calculation of neutralino annihilation into two photons
No full textFor the first time, a full one-loop calculation of the process chi chi --> 2 gamma is performed, where chi is the lightest neutralino in the minimal supersymmetric extension of the Standard Model. This process is of interest for dark matter detection, since it would give a sharp gamma ray line with E-gamma = m(chi). We improve upon and correct published formulas, and give cross sections for supersymmetric models with chi masses between 30 GeV and several TeV. We find a new contribution, previously neglected, which enhances the 2 gamma rate for TeV higgsinos by up to an order of magnitude. As a byproduct, we obtain a new expression for the related process chi chi --> 2 gluons, which on the other hand can be smaller than previously calculated
Spectral gamma-ray signatures of cosmological dark matter annihilations
No full textWe propose a new signature for weakly interacting massive particle (WIMP) dark matter, a spectral feature in the diffuse extragalactic gamma-ray radiation. This feature, a sudden drop of the gamma-ray intensity at an energy corresponding to the WIMP mass, comes from the asymmetric distortion of the line due to WIMP annihilation into two gamma rays caused by the cosmological redshift. Unlike other proposed searches for a line signal, this method is not very sensitive to the exact dark matter density distribution in halos and subhalos
Carbon and nutrient dynamics in natural and Agricultural tropical ecosystem/ L. Bergstrom; H. Kirchmann (edt)
No full textx, 319 hal.: ill.; 24 cm
Carbon and nutrient dynamics in natural and Agricultural tropical ecosystem/ L. Bergstrom; H. Kirchmann (edt)
No full textx, 319 hal.: ill.; 24 cm
Clumpy neutralino dark matter
No full textWe investigate the possibility to detect neutralino dark matter in a scenario in which the galactic dark halo is clumpy. We find that under customary assumptions on various astrophysical parameters, the antiproton and continuum gamma-ray signals from neutralino annihilation in the halo put the strongest limits on the clumpiness of a neutralino halo. We argue that indirect detection through neutrinos from the Earth and the Sun should not be affected much by clumpiness. We identify situations in parameter space where the gamma-ray line, positron and diffuse neutrino signals from annihilations in the halo may provide interesting signals in upcoming detectors
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
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