1,721,429 research outputs found
A Novel Technique to Reconstruct the Mass of the Associated Z boson Decaying into Jets in W+Z and Z+Z Events with Lepton(s), Missing Transverse Energy and Three Jets.
No full textThe study of associated WZ boson production with a lepton and a neutrino signaling the W, and a bb-pair in the final state is important since the event topology of this process is the same as expected for WH associated production of a W and the Standard Model light-Higgs boson (M_{H} lnubb whose rate can be accurately predicted, allows to calibrate and optimize many of techniques used in the SM Higgs search and provides a ``standard candle'' for that crucially important search. In addition, WZ associated production generates a significant background for low mass Higgs Boson searches with H decaying into a bb pair.
At the Tevatron, the process WH-> W bb has an expected cross section about five times lower than WZ->Wbb for m_H~ 120 GeV/c2. Therefore, observing that process would be a benchmark for the even more difficult search for the light Higgs in the WH->Wbb process.
Observing associated WZ production at the Tevatron in the channel WZ->lnubb is extremely difficult for two main reasons.
The event rate is extremely low. A WZ production cross section of ~3.22 pb together with a Z->bb branching ratio of ~15% provides about 50 fb in the WZ->lnubb channel. With a trigger and kinematical selection efficiency of the order of a few %, one expects a handful of events per fb^-1 of integrated luminosity.
This statement remains valid even if the few ZZ events with leptonic decay of one Z are included in the acceptance.
A standard kinematical cut requests exactly two high energy jets (i.e. E_{T}> 20 GeV) in the candidate sample. Simulations show that if a third energetic jet is allowed the signal acceptance is increased by about 1/3. Therefore, it would be very important to be able to extract a Z->bb signal also in events with more than two high energy jets.
A second difficulty is that the signal to background ratio is very poor, due primarily to the contribution of associated production of and incoherent jets. Optimal dijet mass resolution is of utmost importance for discriminating this background, since a fit to the invariant mass distribution of the two jets, associated to the hadronic decay of , is used to disentangle the diboson signal from the backgrounds in the candidate data sample.
In this thesis, we present a search for WZ/ZZ in events with a lepton(s), missing transverse energy and jets. Besides looking at the sample where two exclusive jets are found, we investigate the sample with 3 jets where about the 33% of the signal events lie.
In WZ events, additional jets may be initiated by gluon(s) radiated by the interacting partons (initial state radiation, ISR) or by the Z-decay products (final state radiation, FSR). FSR jets should legitimately be included in the reconstructed Z-mass.
However, the presence of either ISR or FSR jets in a 3-jets events confuses the choice of the jet system to be attributed to Z decay. In this sample the invariant mass of the two E_T-leading jets would normally be chosen to reconstruct the Z boson. To improve both the mass resolution and the sensitivity of the search we describe an alternative procedure to reconstruct the Z-invariant mass. Improving the resolution in such a sample means choosing the correct jet combination for building the Z mass.
My thesis work has been to investigate at generator level a sample of simulated CDF WZ events for finding a means to determine the origin of the extra jet and the right jet combination to be chosen for the best reconstruction of the Z mass. This is attempted for the first time in CDF.
Four different Neural Networks (NNs) have been trained: NN, NN, NN and NN. These NNs should make us to be able to decide event by event which among of the 4 four possible different combinations can be used for building the -mass in the three jets sample. If one jet is due to ISR, we expect one of the MJ1J2, MJ1J3, MJ2J3 combinations to be correct, while if one jet is due to FSR the choice should be MJ1J2J3. NNs combine kinematical information and some tools developed by CDF Collaboration for distinguishing gluon-like and b-like jets from light-flavored jets.
Based on the response of the four NNs, we determine the most likely jet combination for building the Z mass in each event. The method allow to use a different combination from J1J2 in about 50% of cases.
To qualify the potential of the method we have studied an experimental data sample accepting events with a leptonically decaying W and 3 large transverse momentum jets, as in the studies of the simulated WZ sample. The selection cuts accept jets of all flavors (pretag sample), and all diboson events including WW besides WZ, ZZ may pass the cuts. We estimate the probability at three standard deviations level to extract an inclusive diboson signal in the 3-jets sample alone (P). After our procedure for building the Z mass is applied, P is about 4 times greater than when building the Z mass ``by default'' with the two E_{T} leading jets.
The next step would be to discriminate against the WW contribution. A straight ``Higgs like'' approach would be to require b-jets in the events. When one or more jets are required to be b-like (the \emph{tag} sample) our technique, if applied stand-alone, provides only a modest improvement in sensitivity over the option of building the Z-mass from J1J2. Studies for improving the method further are on-going.
However, already now our technique allows including the three jets sample in the WZ/ZZ analyses in order to increase acceptance and sensitivity in the search for the hadronically decaying Z-boson
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
On Proving Safety Properties by Integrating Static Analysis, Theorem Proving and Abstraction
Full text linkion V. Rusu y E. Singerman SRI International, Menlo Park, California, USA Abstract. We present a new approach for proving safety properties of reactive systems, based on tight interaction between static analysis, theorem proving and abstraction techniques. The method incrementally constructs a proof or finds a counterexample. Every step consists of applying one of the techniques and makes constructive use of information obtained from failures in previous steps. The amount of user intervention is limited and is highly guided by the system at each step. We demonstrate the method on three simple examples, and show that by using it one can prove more properties than by using each component as a stand-alone. 1 Introduction Theorem proving [GM95, ORS+95, CCF+97] 1 is a powerful and general way to verify safety properties of reactive systems, but its use in mechanical verification requires a serious amount of both insightful and labor-intensive manual guidance from the human verifier..
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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