1,721,910 research outputs found
The pixel detector based tracklet reconstruction algorithm in ALICE
No full textThis note describes a method to reconstruct signals in the two silicon pixel detector layers compatible with tracks coming from the main interaction vertex, namely tracklets. The basic algorithm strategy and its performance are illustrated
Anomalous Broadening of Jet-Peak Shapes in Pb-Pb Collisions and Characterization of Monolithic Active Pixel Sensors for the ALICE Inner Tracking System Upgrade
No full textTwo-particle angular correlations are presented from Pb-Pb and pp collisions at 2.76 TeV. These measurements are powerful tools to study jets in a transverse momentum regime where they cannot be reconstructed over the large fluctuating background produced in heavy-ion collisions. In these studies, the distribution of azimuthal angle (Δφ) and pseudorapidity (Δη) differences of particle pairs is calculated. Jets manifest themselves as a peak around (Δφ, Δη) = (0, 0) and as a structure elongated in Δη at Δφ = π. The jet peak is studied as a function of transverse momentum and centrality in Pb-Pb collisions, and it is compared to pp collisions and to results from A Multi-Phase Transport model (AMPT). In Pb-Pb collisions, an asymmetric broadening of the jet peak towards central collisions at low transverse momentum is found, and in addition an unexpected depletion around (Δφ, Δη) = (0, 0) is observed. The comparison to AMPT suggests that the two effects are connected to large radial and longitudinal flow, therefore they can arise from an interplay of the jets with the flowing medium produced in the collisions of heavy-ions. The measurements are done by the ALICE detector, which will be upgraded during the second long shutdown of the LHC in 2019-2020. During this upgrade, the Inner Tracking System of ALICE will be replaced by a detector consisting of seven concentric layers of Monolithic Active Pixel Sensors. The prototypes of this detector and the setup used for their characterization are discussed in details. Tests at test beam facilities are carried out on unirradiated sensors and irradiated sensors are tested as well to study the long term functionality of the detector. The results of these measurements are presented, and it is found that the prototypes fulfill the requirements of the upgrade in terms of detection efficiency, spatial resolution and noise occupancy both before and after irradiation, making them suitable for the operation in the environment in the ALICE experiment
The CERN analysis facility: a PROOF cluster for day-one physics analysis
No full textALICE (A Large Ion Collider Experiment) at the LHC plans to use a PROOF cluster at CERN (CAF - CERN Analysis Facility) for analysis. The system is especially aimed at the prototyping phase of analyses that need a high number of development iterations and thus require a short response time. Typical examples are the tuning of cuts during the development of an analysis as well as calibration and alignment. Furthermore, the use of an interactive system with very fast response will allow ALICE to extract physics observables out of first data quickly. An additional use case is fast event simulation and reconstruction. A test setup consisting of 40 machines is used for evaluation since May 2006. The PROOF system enables the parallel processing and xrootd the access to files distributed on the test cluster. An automatic staging system for files either catalogued in the ALICE file catalog or stored in the CASTOR mass storage system has been developed. The current setup and ongoing development towards disk quotas and CPU fairshare are described. Furthermore, the integration of PROOF into ALICE's software framework (AliRoot) is discussed
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
Anomalous Broadening of Jet-Peak Shapes in Pb-Pb Collisions and Characterization of Monolithic Active Pixel Sensors for the ALICE Inner Tracking System Upgrade
No full textTwo-particle angular correlations are presented from Pb-Pb and pp collisions at 2.76 TeV. These measurements are powerful tools to study jets in a transverse momentum regime where they cannot be reconstructed over the large fluctuating background produced in heavy-ion collisions. In these studies, the distribution of azimuthal angle (Δφ) and pseudorapidity (Δη) differences of particle pairs is calculated. Jets manifest themselves as a peak around (Δφ, Δη) = (0, 0) and as a structure elongated in Δη at Δφ = π. The jet peak is studied as a function of transverse momentum and centrality in Pb-Pb collisions, and it is compared to pp collisions and to results from A Multi-Phase Transport model (AMPT). In Pb-Pb collisions, an asymmetric broadening of the jet peak towards central collisions at low transverse momentum is found, and in addition an unexpected depletion around (Δφ, Δη) = (0, 0) is observed. The comparison to AMPT suggests that the two effects are connected to large radial and longitudinal flow, therefore they can arise from an interplay of the jets with the flowing medium produced in the collisions of heavy-ions. The measurements are done by the ALICE detector, which will be upgraded during the second long shutdown of the LHC in 2019-2020. During this upgrade, the Inner Tracking System of ALICE will be replaced by a detector consisting of seven concentric layers of Monolithic Active Pixel Sensors. The prototypes of this detector and the setup used for their characterization are discussed in details. Tests at test beam facilities are carried out on unirradiated sensors and irradiated sensors are tested as well to study the long term functionality of the detector. The results of these measurements are presented, and it is found that the prototypes fulfill the requirements of the upgrade in terms of detection efficiency, spatial resolution and noise occupancy both before and after irradiation, making them suitable for the operation in the environment in the ALICE experiment
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
Jet-like two-particle correlations in p-Pb collisions
No full textThe thesis presents the first measurements of the yields of jet-like structures at low transverse momentum in p-Pb collisions. A statistical method known as two-particle correlations is used to overcome the difficulties in identifying such structures with standard jet-reconstruction algorithms. Moreover, a subtraction procedure has been developed to disentangle the jet-like contribution from the long-range correlations structures (so-called 'double ridge') found in p-Pb collisions, which are attributed to collective phenomena.Through the study of jet-like structures, this method allows to estimate the number of independent sources of particle production, proportional to the number of multiparton interactions in PYTHIA simulations
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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