1,721,813 research outputs found
The OPERA experiment at Gran Sasso
No full textOPERA (Oscillation Project with Emulsion tRacking Apparatus) is a long baseline neutrino experiment aiming to detect for the first time the appearance of tau neutrinos in a pure muon neutrino beam. The OPERA detector is exposed to the CNGS beam (CERN Neutrinos to Gran Sasso), a high-intensity and high-energy beam of muon neutrinos produced at the CERN SPS and directed toward the Gran Sasso underground laboratory (LNGS), 730 km away. The LNGS laboratory is situated under an average depth of 3800 meters water equivalent, making OPERA the deepest experiment able to measure cosmic ray muons with a magnetized detector, e.g. the cosmic ray muon charge ratio. Cosmic ray events were observed, together with the first neutrino beam events, during the 2007 and 2008 CNGS runs. This paper reviews the experimental apparatus, presents the first results for neutrino data and describes the analysis of cosmic ray data. © 2009 Elsevier B.V. All rights reserved
Measurement of the TeV atmospheric muon charge ratio with the full OPERA data set
No full textAbstractThe OPERA detector, designed to search for νμ→ντ oscillations in direct appearance mode, is located in the underground Gran Sasso laboratory, a privileged location to study TeV-scale cosmic rays. Given the large rock depth and the detector's wide acceptance, the apparatus was used to measure the atmospheric muon charge ratio in the TeV energy region. The muon charge ratio, defined as the number of positive over negative charged muons, provides an understanding of the mechanism of multiparticle production in the atmosphere in kinematic regions not accessible to accelerators, as well as information on the primary cosmic ray composition. We present the results obtained with the full statistics collected by OPERA from 2008 to 2012. The combination of two data sets with opposite magnet polarities allows minimizing systematic uncertainties and reaching an accurate determination of the muon charge ratio. Relevant parameters on the composition of primary cosmic rays and the associated kaon production in the forward fragmentation region are obtained
Results from the OPERA experiment at the CNGS beam
Full text linkThe OPERA experiment at the Gran Sasso underground laboratory was designed to study vμ → vτ oscillations in appearance mode in the CNGS neutrino beam. Five vτ candidate events have been observed, allowing to assess the discovery of vμ → vτ transitions in the atmospheric sector with a significance of 5.1σ. In this paper the vτ data analysis will be discussed, with emphasis on the background constraints obtained using dedicated data-driven control samples. Results on the search for vμ → vτ oscillations, on the search for sterile neutrino mixing and on the atmospheric muon charge ratio will also be presented
Highlights from the OPERA experiment
No full textThe OPERA neutrino experiment is designed to detect νμ → ντ oscillations in direct appearance mode. The hybrid apparatus consists of an emulsion/lead target complemented by electronic detectors. It is placed in the long-baseline CERN to Gran Sasso neutrino beam (CNGS) 730 km away from the source. The running of the experiment and the extraction of data recorded in the emulsion will be described, together with the special procedures used to locate interaction vertices and detect short decay topologies. New oscillation search results with increased statistics will be presented. Up-to-date results of the neutrino velocity measurements will also be reported
Experimental results on the atmospheric muon charge ratio
No full textThe atmospheric muon charge ratio, defined as the number of positive over negative charged muons, is a highly informative observable both for cosmic rays and particle physics. It allows studying the features of high-energy hadronic interactions in the forward region and the composition of primary cosmic rays. In this review results from underground experiments measuring the charge ratio around 1 TeV are discussed. The measurements in the TeV energy region constrain the associated kaon production, which is particularly important e.g. for the calculation of the atmospheric neutrino flux
Search for sterile neutrino mixing in the νμ → ντ appearance channel with the OPERA detector
No full textThe OPERA experiment has observed muon neutrino to tau neutrino oscillations in the atmospheric sector in appearance mode. Five ντ candidate events have been detected, a number consistent with the expectation from the “standard” 3ν framework. Based on this result new limits on the mixing parameters of a massive sterile neutrino have been set. The analysis is performed in the 3+1 neutrino model
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
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