1,723,083 research outputs found
Search for vector-like quarks in events with two oppositely charged leptons and jets in proton–proton collisions at sqrt(s) = 13 TeV s = 13 Te
No full textA search for the pair production of heavy vector-like partners and of the top and bottom quarks has been performed by the CMS experiment at the CERN LHC using proton–proton collisions at . The data sample was collected in 2016 and corresponds to an integrated luminosity of 35.9. Final states studied for production include those where one of the quarks decays via and the other via , , or , where is a Higgs boson. For the case, final states include those where one of the quarks decays via and the other , , or . Events with two oppositely charged electrons or muons, consistent with coming from the decay of a boson, and jets are investigated. The number of observed events is consistent with standard model background estimations. Lower limits at 95% confidence level are placed on the masses of the and quarks for a range of branching fractions. Assuming 100% branching fractions for , and , and quark mass values below 1280 and 1130, respectively, are excluded
Strategies and performance of the CMS silicon tracker alignment during LHC Run 2
No full textThe strategies for and the performance of the CMS silicon tracking system alignment during the 2015–2018 data-taking period of the LHC are described. The alignment procedures during and after data taking are explained. Alignment scenarios are also derived for use in the simulation of the detector response. Systematic effects, related to intrinsic symmetries of the alignment task or to external constraints, are discussed and illustrated for different scenarios
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
Results on Top Physics by CMS
Full text linkIn this talk, several measurements in the top-quark sector are presented, obtained from the CMS data collected in 2011 and 2012 at centre-of-mass energies of 7 and 8 TeV. The production cross section of ttbar pairs is measured in several decay channels lepton+jets, dilepton and fully hadronic channels, including channels with the tau lepton. Differential cross sections are measured and are provided as a function of various kinematic observables; the results are compared with precise theory calculations. Measurements of several top-quark properties are reported, including the top pair charge asymmetry, the W helicity in top decays, the measurement of the production of ttbar pairs with W, Z, gamma, the spin correlation and the search for anomalous couplings and flavor-changing neutral currents. The results are compared with predictions from the standard model as well as new physics models. The cross sections for the electroweak production of single top quarks are measured in the t-channel and in association with W-bosons. Measurements of top-quark properties in single top quark production are also presented. The results include the W-helicity in top quark decays and the searches for the s-channel production and anomalous couplings
A deep neural network to search for new long-lived particles decaying to jets
No full textA tagging algorithm to identify jets that are significantly displaced from the proton-proton (pp) collision region in the CMS detector at the LHC is presented. Displaced jets can arise from the decays of long-lived particles (LLPs), which are predicted by several theoretical extensions of the standard model. The tagger is a multiclass classifier based on a deep neural network, which is parameterised according to the proper decay length ct 0 of the LLP. A novel scheme is defined to reliably label jets from LLP decays for supervised learning. Samples of pp collision data, recorded by the CMS detector at a centre-of-mass energy of 13 TeV, and simulated events are used to train the neural network. Domain adaptation by backward propagation is performed to improve the simulation modelling of the jet class probability distributions observed in pp collision data. The potential performance of the tagger is demonstrated with a search for long-lived gluinos, a manifestation of split supersymmetric models. The tagger provides a rejection factor of 10 000 for jets from standard model processes, while maintaining an LLP jet tagging efficiency of 30%-80% for gluinos with 1 mm≤ct 0≤ 10 m. The expected coverage of the parameter space for split supersymmetry is presented
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