1,721,511 research outputs found
Integration and Commissioning of the Front-End Electronics of NSW ATLAS small-strip Thin Gap Chambers
No full textThe ATLAS Muon Spectrometer is going through an extensive Phase I upgrade to cope up with the future LHC runs of high luminosity of up to . The innermost and first station of the Muon end cap system, the Small Wheel, will be replaced by the New Small Wheel, which has high trigger and precision tracking capabilities. This is achieved by a combination of two detector technologies, Small-Strip Thin Gas Chamber (sTGC) and Micro Mesh Gaseous structures (MM). MM is used for the precision tracking and sTGC is used as a primary trigger detector because of its timing resolution (drift time of most electrons shorter than one bunch crossing period (25 ns) and the front-end ASICs (Application Specific Integrated Circuit), VMMs, can make measurement with precision of 2 ns along with the amplitude measurement). Our team is working extensively on the integration and commissioning of the front-end electronics for the sTGC chambers. Considering the complexity of the system we are dealing with, we are working to resolve many challenges to test large number of physical channels ( 354K) with three different types – pads, strips and wires and ASICs (more than 11K) . We will present our experiences with the trigger and the readout tests of the electronics
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 compressed scalar top quark pairs in p-p collisions at LHC at
No full textSupersymmetry (SUSY) is one of the most appealing theories, which tries to explain some of the experimental and theoretical shortcomings of the Standard Model. It tries to solve the Hierarchy problem by introducing new particles (supersymmetric partners of the Standard Model particles). The quantum corrections due to these particles cancel the divergent contribution from the SM particles to the Higgs mass calculation. The top quark couples to the Higgs maximally due to its higher mass. Therefore, particularly, the supersymmetric partner of the top quark- scalar top quark(stop) is interesting for the searches to stabilize the Higgs mass. It is not easy to single out a model in supersymmetry due to the large number of free parameters. So, theorists have come up with some simplified models, which can be tested experimentally. This thesis is based on one of such models, where a stop decays to a top quark and a neutralino, where neutralino is assumed to be the Lightest Supersymmetric Particle (LSP). It is weakly interacting and stable. Hence, it does not leave any trace in the detector contributing to the missingtransverse energy (MET) in the event. This additional source of MET differentiates the signature of background from the signature of the signal events. Some of the popular MET based analyses have been successful in excluding stop particles upto the mass of 900 GeV. But, the lower mass regions still have weaker exclusion limits. Especially,the region in the stop-LSP mass plane described by , contains some model with lower stop masses, which have not been excluded yet due to the limitations of the currentMET based searches. By selecting only the events with a hard ISR (Initial State Radiation) jet, the MET of the entire system can be improved and also the lower mass models can be probed. For the events produced using the Monte Carlo simulations, expected upper limits at 95% confidence level were calculated for the integrated luminosity L = 30 , 35.9 and 100 at of centre of mass energy. These limits exclude stop masses in the range 225 < 450. Forthe lower masses of LSP, another technique based on the fermionic and bosonic nature of the t and , respectively, is used to study the effect of the spin correlations between the decay products of the top or stop pair produced. A dileptonanalysis can be used to study (l1 , l2 ) distributions (l1and l2 are the two leptons) and calculating the limits using the events in (l1 , l2 ) bins, give betterexclusion potential for the models with < 225 GeV compared to that given by the full hadronic ISR tagging analysis
Observations of the Radiation Amplitude Zero effect and of the Diboson Longitudinal-Longitudinal Interactions in High Region using W±Z Production with the ATLAS Detector
No full textThis thesis focuses on the studies of di-boson polarization states in W±Z production, presenting two novel measurements using pp collisions at a center-of-mass energy of = 13 TeV. The WZ decaying to leptonic final states is considered. The data was collected at the Large Hadron Collider (LHC) with the ATLAS experiment, utilizing an integrated luminosity of 140.1 fb−1 . The first measurement pertains to the Radiation Amplitude Zero effect. By studying the depth of distributions involving the rapidity differences between the W lepton and the Z boson (∆Y3Z) and between the W boson and the Z boson (∆YWZ), an agreement is observed between the measured depth in the background-subtracted data consisting only of the transverse-transverse WZ contribution and the Monte Carlo (MC) prediction. The second measurement involves the determination of the longitudinal-longitudinal WZ polarization fraction. This measurement is performed in regions with predominantly s-channel WZ events, characterized by high values in two fiducial phase spaces: > 100 GeV or > 200 GeV. To extract the polarization fraction, a multivariate analysis based on a Boosted Decision Trees discriminant is employed. A maximum log-likelihood fit is then executed, yielding a longitudinal-longitudinal polarization fraction (00) of 0.25+0.06 −0.06 for the > 200 GeV region, with an observed (expected) significance of 3.4σ (4.6σ). In the p > 100 GeV region, the longitudinal-longitudinal polarization fraction is found to be 0.17+0.021 −0.022, with an observed (expected) significance of 7.9σ (8.8σ). Notably, this marks the first measurement of the longitudinal-longitudinal WZ production in the high- phase space. In addition to the analysis, this thesis covers the contribution of the University of Michigan ATLAS group to the ATLAS New Small Wheel Muon Spectrometer upgrade, particularly the integration and commissioning of the small-strip Thin Gap Chambers electronics. Detailed procedure regarding the integration work, especially the readout chain electronics validations, and detector noise studies is described in the thesis
A highlight of multiboson interactions, their polarization and photon-induced access to tau g-2 at ATLAS
No full textMeasurements of multiboson production at the LHC are fundamental probes of the electroweak gauge structure of the Standard Model. With the large data samples from the LHC, processes involving quartic gauge boson couplings are now accessible. In this talk we present recent ATLAS results of quartic interactions including measurements with three gauge bosons in the final state. These results are interpreted via an Effective Field Theory analysis of anomalous quartic gauge self-interaction. In addition we will present a first measurement of di-boson polarization at the LHC. Finally, we will show how high statistics measurements of photon-induced tautau production in lead-lead collisions provide a precise and unique opportunity to investigate fundamental parameters like tau lepton's anomalous magnetic dipole moment
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
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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