1,720,981 research outputs found
Search for the Standard Model Higgs boson in association with top quarks and decaying to at TeV using the ATLAS detector
No full textA search for a Higgs boson produced in association with a pair of top quarks and decaying into apair of b quarks is presented. The analysis uses an integrated luminosity of 4.7 fb−1 of pp collisions at a center-of-mass energy of = 7 TeV collected in 2011 with the ATLAS detector at the LHC. The search is focused on the semileptonic decay of the tbar t system and combines nine different topologies given by the jet and b-tagged jet multiplicities of the event. A kinematic reconstruction of the Higgs boson mass is performed in the signal enhanced region, which becomes the primary discriminant variable between signal and background. Background-dominated samples are exploited to constrain the leading systematic uncertainties affecting the background prediction. No significant excess of events above the background expectation is observed. For a Higgs boson with a mass of 125 GeV, an observed (expected) 95% confidence upper limit of 13.1 (10.5) times the Standard Model cross section is obtained
A likelihood-based reconstruction algorithm for top-quark pairs and the KLFitter framework
No full textA likelihood-based reconstruction algorithm for arbitrary event topologies is introduced and, as an example, applied to the single-lepton decay mode of top-quark pair production. The algorithm comes with several options which further improve its performance, in particular the reconstruction efficiency, i.e., the fraction of events for which the observed jets and leptons can be correctly associated with the final state particles of the corresponding event topology. The performance is compared to that of well-established reconstruction algorithms using a common framework for kinematic fitting. This framework has a modular structure which describes the physics processes and detector models independently. The implemented algorithms are generic and can easily be ported from one experiment to another. (C) 2014 Elsevier B.V. All rights reserve
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
Search for tt(H→bb) using the ATLAS detector at 8 TeV
No full textA search for the Standard Model Higgs boson produced in association with a pair of top quarks, , is presented. The analysis uses 20.3 fb of pp collision data at = 8 TeV, collected with the ATLAS detector at the Large Hadron Collider during 2012. The search is designed for the H to decay mode and uses events containing one or two electrons or muons. In order to improve the sensitivity of the search, events are categorised according to their jet and b-tagged jet multiplicities. A neural network is used to discriminate between signal and background events, the latter being dominated by +jets production. In the single-lepton channel, variables calculated using a matrix element method are included as inputs to the neural network to improve discrimination of the irreducible + background. No significant excess of events above the background expectation is found and an observed (expected) limit of 3.4 (2.2) times the Standard Model cross section is obtained at 95% confidence level. The ratio of the measured signal cross section to the Standard Model expectation is found to be = 1.5 1.1 assuming a Higgs boson mass of 125 GeV
Search for the Standard Model Higgs boson produced in association with and decaying into at TeV with the ATLAS detector using the Matrix Element Method
No full textA search for the Standard Model Higgs boson produced in association with a pair of top quarks () is presented. The analysis uses 20.3 fb of collision data at TeV, collected with the ATLAS detector at the Large Hadron Collider during 2012. The search is designed for the decay mode and is performed in the single lepton (electrons or muons) decay channel of the top quark pair. In order to improve the sensitivity of the search, events are categorised according to their jet and -tagged jet multiplicities into nine different analysis regions. A matrix element method is developed and applied to regions with six jets to obtain discriminants separating events from the irreducible background. In signal-enriched regions, a neural network is employed combining kinematic variables and variables obtained from the matrix element method to maximise the separation between signal and background events. The nine analysis regions are statistically combined using a profile likelihood fit to improve the background predictions and reduce the systematic uncertainties. The ratio of the measured signal cross section to the Standard Model expectation is found to be assuming a Higgs boson mass of 125 GeV. No significant excess of events above the background expectation is found and an observed (expected) limit of is set at 95% confidence level. The single lepton channel is combined with the dilepton channel of the decay resulting in and an observed (expected) upper limit of 3.4 (2.2) times the Standard Model cross section at 95% confidence level
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
Search for the Standard Model Higgs boson produced in association with tt and decaying into bb at 8 TeV with the ATLAS detector using the Matrix Element Method
Full text linkA search for the Standard Model Higgs boson produced in association with a pair of top quarks (ttH) is presented. The analysis uses 20.3 fb−1 of pp collision data at √s = 8 TeV, collected with the ATLAS detector at the Large Hadron Collider during 2012. The search is designed for the H → bb decay mode and is performed in the single lepton (electrons or muons) decay channel of the top quark pair. In order to improve the sensitivity of the search, events are categorised according to their jet and b-tagged jet multiplicities into nine different analysis regions. A matrix element method is developed and applied to regions with six jets to obtain discriminants separating ttH events from the irreducible tt+ bb background. In signal-enriched regions, a neural network is employed combining kinematic variables and variables obtained from the matrix element method to maximise the separation between signal and background events. The nine analysis regions are statistically combined using a profile likelihood fit to improve the background predictions and reduce the systematic uncertainties. The ratio of the measured ttH signal cross section to the Standard Model expectation is found to be µ = 1.2 ± 1.3 assuming a Higgs boson mass of 125 GeV. No significant excess of events above the background expectation is found and an observed (expected) limit of µ < 3.6 (2.6) is set at 95% confidence level. The single lepton channel is combined with the dilepton channel of the tt decay resulting in µ = 1.5 ± 1.1 and an observed (expected) upper limit of 3.4 (2.2) times the Standard Model cross section at 95% confidence level
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
Searches for Vector-Like Quarks at 13 TeV at the ATLAS Experiment
No full textVector like quarks appear in many theories beyond the Standard Model as a way to cancel the mass divergence for the Higgs boson. The current status of the ATLAS searches for the production of vector like quarks will be reviewed for proton-proton collisions at 13 TeV. This presentation will address the analysis techniques, in particular the selection criteria, the background modeling and the related experimental uncertainties
- …
