1,721,137 research outputs found
Searches for Doubly Charmed Baryons at LHCb
Get PDFThe results of two separate searches for the doubly-charmed particle through the → K−++ and → D+pK−+ decay modes are presented in this thesis. Both analyses examine proton-proton collision data collected by the LHCb detector at the European Laboratory for Particle Physics. The → K−++ analysis resulted in the first-ever observation of a doubly-charmed baryon, namely the state. Using data recorded in 2016 at LHCb, the mass of the state was measured to be () = 3621.40 ± 0.72 (stat) ± 0.27 (syst) ± 0.14 () MeV/c, where the first and second uncertainties are statistical and systematic, respectively, and the last uncertainty is due to the limited knowledge on the mass of the baryon. The signal was determined to be compatible with a weak decay. The second analysis did not yield any evidence of the → D+pK−+ decay within the data recorded in 2016 so, instead, the following branching fraction ratio upper limit is set B( → D+pK−+)/B( → K−++) < 1.7 (2.1) × 10 at the 90% (95%) confidence level and at the measured mass of the particle from the → K−++ analysis. No signal is observed in the mass range 3300−3800 MeV/c. Additionally, a new multivariate-based trigger line was developed for reconstructing → pK−+ decays at LHCb. The new trigger makes use of the Bonsai Boosted Decision Tree method and is designed with searches for doubly-charmed particles in mind. This trigger gives a 36% increase in the signal yield of potential particles compared to an original trigger line that was designed for the similar purposes. Aside from searches for doubly-charmed baryons, a short study is conducted into the calibration of the Ring Imaging Cherenkov (RICH) subdetectors at the LHCb detector. A method was successfully developed to obtain high momentum tracks without any knowledge of the magnetic field, which will be used in the future to test the hypothesis that the magnetic field is causing discrepancies seen between data and simulation for the RICH-1 Cherenkov angle resolution
decays and properties
No full textThe particles are baryons contains 2 constituent charm quarks in their structure which are expected to decay to high multi-body final states. The LHCb detector is ideally designed for studies of them due to its excellent particle identification and vertex reconstruction. Its capabilities in this area of physics was firmly demonstrated when LHCb announced the discovery of the first ever doubly charmed baryon, , in decays of in 2017. This doubly charmed baryon was observed as a highly significant structure in the mass spectrum from proton-proton collision data recorded by the LHCb detector in Run2. A yield of 313 33 candidates is measured and the local significances is in excess of 12 in the 13 TeV data. The properties of the peak suggest it is inconsistent with being a strongly decaying state. From the 13 TeV data, the mass is measured to be . More analyses in the doubly charmed baryon sector using LHCb data are now well advanced. This includes, but is not limited to, searches for the singly charged state as well as the lifetime measurement of the state
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
- …
