1,721,457 research outputs found
Charmonium production at LHCb: measurement of the to production ratio with the first data
No full textLHCb is an experiment dedicated to precise measurements of CP violating and rare decays of -hadrons. It will exploit the proton-proton collisions at an energy of 14 TeV in the centre-of-mass system, produced by the LHC collider (CERN-Geneva), and will operate at a luminosity of . The expected number of pairs produced by the LHC collisions is . LHCb is designed with a robust and efficient trigger whose purpose is to reduce the event rate in input () to a manageable event rate, enriched in content of heavy flavour quarks, to be written to storage (). The rate reduction is achieved in two trigger levels, L0 (Level 0) and HLT (High Level Trigger), that will be widely discussed in this thesis. A good particle identification as well as efficient tracks and vertexes reconstruction, are fundamental requirements for the reconstruction of the -hadron decays and proper time measurement. LHCb aims to improve the current precision on the CKM parameters and to search for any possible inconsistency with the Standard Model predictions in order to find out eventual "New Physics" effects. The LHCb detector is fully installed, commissioned and ready for data taking: the LHC start-up is expected by the end of 2009. In the first periods of data taking, the understanding of the apparatus, as well as the preparatory measures, are necessary steps for the future analyses on the -hadrons. In particular the charmonium states will be largely produced either as prompt or from transitions.Their well known properties make these resonances ideal for alignment and calibration studies. On the other hand the observation of charmonium states and the measurement, per example, of the prompt cross section ratio between and can give some interesting informations about the production mechanisms. The hadroproduction of and is not yet completely understood. Early models could not describe the cross section of directly produced mesons. Such models underestimated the measurements by a factor of approximately 50 and did not adequately describe the cross section shape as a function of . With the advent of Non-Relativistic QCD (NRQCD) it has been possible to give a better theoretical description of charmonium production through the introduction of the Color Octet model. Nevertheless there are still a lot of issues and open problems: the spin alignment of mesons predicted by NRQCD theories is totally in disagreement with the CDF findings (polarization puzzle); moreover recent NL0 and NNL0 calculations in the Color Singlet model have shown that the amount of the Color Octet needed so far to explain data could be overestimated. Further measurements with and other charmonia states are needed to discriminate between the models and clarify the situation. In this thesis the measurement of the prompt cross section ratio between and , with the first data of LHCb, is described. Simulation studies have been performed to assess the acceptances, the efficiencies and the systematic errors introduced by the apparatus. Particular emphasis is given to the polarization of the and to the systematic induced. This measure is a starting point for the subsequent absolute cross section measurements. In chapters I-II-III of this thesis essentially we give a detailed description of the LHCb experiment including the trigger and the online monitoring system. In chapter IV we discuss the theory of charmonium production and the expectations at LHCb. In the chapters V-VI, we present a study on Monte Carlo data in which the measurement of the prompt cross section ratio between and , in the dimuon channel, is described. Finally, in the chapter VII we will discuss some further prospects on charmonium measurements
Honey, a palatable substance for infants: from De Rerum Natura to evidence-based medicine
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Occurrence of platinum, palladium and gold in pine needles of Pinus pinea L. from the city of Palermo (Italy)
No full textPreliminary data on the presence of Pt, Pd and Au in airborne particulate matter from the urban area of Palermo (Sicily, Italy) are presented. They were obtained by analysing 40 samples of pine needles (Pinus pinea L.) collected in and around the city. Observed concentrations range from 1 to 102 μg/kg for Pt, 1 to 45 μg/kg for Pd and 22 to 776 μg/kg for Au. Platinum and Pd concentrations in pine needles are up to two orders of magnitude higher than their crustal abundances. They exhibit a high statistical correlation (R2=0.74) which suggests a common origin. Precious metal concentrations measured within the city centre are much higher than those occurring outside the town. The distribution patterns of Pt and Pd in the study area are compared to the distributions of Au and Pb. Gold is enriched at the same sites where Pt and Pd are enriched, while Pb shows some discrepancies. The most probable local source of all of these elements is traffic, Average Pt and Pd emissions in the city area are estimated to be about 136 and 273 g/a, respectively. This study supports the use of pine needles as biomonitors of PGE in the environment
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
Pottery production of the Pittore di Lipari: chemical and mineralogical analysis of the pigments
No full textOne of the most impressive Sicilian pottery production is attributed to the so-called Pittore di Lipari, famous for his numerous vessels – found in the archaeological site of Lipari (Eolian Island – Sicily) – decorated with characteristic blue, red and white figures.
From the archaeological point of view, these vessels keep open many questions concerning dating, production technique and cultural background. The chronology proposed by Trendall (Trendall, 1967) – who dated these potteries to the last quarter of the IV B.C. – is questioned on the basis of field observations by Bernabo Brea and Cavalier, who suggest a more recent production (Cavalier, 1976). In this context, new data on the manufacture techniques and on the raw materials used for the pigments may contribute to a deeper comprehension (Mastelloni, 2015; Quartieri et al., 2015).
The importance of the vessels, exposed in the Archaeological Museum of Lipari, imposed the use of non-destructive and in situ methods. Specifically, here we present the results of the mineralogical analysis performed by portable Raman spectroscopy (I- Raman Plus - BWTECH) and the chemical data obtained by a portable XRF (Titan System - Bruker).
The results of this study testify the use of a series of different pigments. Among these, only the white one is made by kaolin and gypsum, suggesting the use of a local supply. The blue portions are probably made by Egyptian blue, while two types of pigments were employed for red colors: ochre for the brown-reddish hues and cinnabar for the red purple nuance. The latter one is reported for the first time in the decoration of pottery, while its use is known in Sicilian and Roman wall paintings. Interestingly, the use of cinnabar suggests commercial and cultural relationships between Lipari and the Etruria area, or, subordinately, with Spain, where this mineral was quarried on the Carthaginian and Roman Republican periods.
References
Cavalier, M. (1976):Nouveauxdocumentssur l'art duPeintre de Lipari, Naples, Bretschneider, 66 p.
Mastelloni, M.A. (2015): I Pittori di Lipari, delle tre Nikai e di Falcone: l'apporto delle analisi alla ricerca.in“Lipára ed il teatro in età tardo classica ed ellenistica”, Palermo, 73-75.
Quartieri, S., Sabatino, G., Di Bella, M., Gianesella, M., Ardizzone, F., Mastelloni, M.A. (2015): Analisi non distruttive sui pigmenti di materiali prodotti a Lipari tra fine IV e I metà III sec. a.C.. in“Lipára ed il teatro in età tardo classica ed ellenistica”, Palermo.
Trendal, A.D. (1967): The red-figured vases of Lucania, Campania and Sicily, Oxford, 700 p
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