Search For The Production Of The Standard Model Z Boson In Association With W Boson In P Anti P Collisions At 196 Tev Center Of Mass Energy
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| Total Pages | : 162 |
| Release | : 2010 |
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The search for the production of the Standard Model Z boson in association with a W boson is motivated and discussed. This is performed using 4.3 fb−1 of Tevatron Run II data collected with the CDF detector in (square root)s = 1.96 TeV proton anti-proton collisions. This is a signature-based analysis where the W boson decays semileptonically into a high-P{sub T} electron or muon plus a neutrino, and where the Z boson decays into two b quark jets (b-jets). We increase the signal-to-background ratio by identifying the b-quarks in the jets with a new neural network-based algorithm. Another neural network then uses kinematic information to distinguish WZ to further increase the signal-to-background ratio. Since our sensitivity is still not enough to achieve an observation, we set a 95% Confidence Level upper limit on the product of the WZ production cross section and its branching fraction to the decay products specified above, and express it as a ratio to the theoretical Standard Model prediction. The resulting limit is 3.9 x SM (3.9 x SM expected).
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| Total Pages | : 7 |
| Release | : 2009 |
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We present a search for exclusive Z boson production in proton-antiproton collisions at √s = 1.96 TeV, using the CDF II detector at Fermilab. We observe no exclusive Z → l+l− candidates and place the first upper limit on the exclusive Z cross section in hadron collisions, [sigma]{sub excl}(Z) 0.96 pb at 95% confidence level. In addition, we observe eight candidate exclusive dilepton events from the quantum electrodynamic process p{bar p} → p[gamma][gamma]{bar p} → pl+l− {bar p}, and measure the cross section for M{sub l{ell}} 40 GeV=c2 and.
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| Total Pages | : 7 |
| Release | : 2009 |
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We present a search for exclusive Z boson production in proton-antiproton collisions at √s = 1.96 TeV, using the CDF II detector at Fermilab. We observe no exclusive Z → ll− candidates and place the first upper limit on the exclusive Z cross section in hadron collisions,?{sub excl}(Z) 0.96 pb at 95% confidence level. In addition, we observe eight candidate exclusive dilepton events from the quantum electrodynamic process p{bar p} → p??{bar p} → pl+l− {bar p}, and measure the cross section for M{sub l{ell}} 40 GeV=c2 and.
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| Release | : 2015 |
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Production of the [Upsilon](1S) meson in association with a vector boson is a rare process in the standard model with a cross section predicted to be below the sensitivity of the Tevatron. Observation of this process could signify contributions not described by the standard model or reveal limitations with the current nonrelativistic quantum-chromodynamic models used to calculate the cross section. We perform a search for this process using the full Run II data set collected by the CDF II detector corresponding to an integrated luminosity of 9.4 fb-1. Our search considers the [Upsilon]→[mu][mu] decay and the decay of the W and Z bosons into muons and electrons. Furthermore, in these purely leptonic decay channels, we observe one [Upsilon]W candidate with an expected background of 1.2±0.5 events, and one [Upsilon]Zcandidate with an expected background of 0.1±0.1 events. Both observations are consistent with the predicted background contributions. The resulting upper limits on the cross section for [Upsilon]+W/Zproduction are the most sensitive reported from a single experiment and place restrictions on potential contributions from non-standard-model physics.
| Author | : Shan-Huei S. Chuang |
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| Total Pages | : 216 |
| Release | : 2007 |
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| Author | : Eric Michael Flattum |
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| Total Pages | : 368 |
| Release | : 1996 |
| Genre | : Proton-antiproton interactions |
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| Total Pages | : 181 |
| Release | : 2007 |
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This dissertation describes a test of the Standard Model (SM) of particle physics by measuring the probability, or cross section, of simultaneously producing a W boson and a Z boson from proton-antiproton collisions. The SM predicts the cross section of WZ production to be 3.68 ± 0.25 pb. The SM and physics of WZ production are described in Chapter 2 of this dissertation. The 1.96 TeV center-of-mass energy proton-antiproton collisions are provided by the Fermi National Accelerator Laboratory (FNAL) Tevatron Collider. The W and Z particles are detected using the D0 detector, which is described in Chapter 3. The data were collected by the detector during 2002-2006 corresponding to 1 fb−1 of p{bar p} collisions. This data set is described in Chapter 6. The measurement uses the trilepton (e[nu]ee, [mu][nu]ee, e[nu][mu][mu], and [mu][nu][mu][mu]) decay channels, in which a W decays to a charged lepton plus a neutrino and a Z decays to a pair of charged leptons. The W and Z particle selection criteria, detection efficiency, and background determination are described in Chapter 7. We observe 13 candidate events in 1 fb−1 of p{bar p} collisions. In this data set we expect to see 4.5 ± 0.6 background events, and we expect to see 9.2 ± 1.0 signal events. The probability of 4.5 ± 0.6 background events to fluctuate to 13 or more events is 1.2 x 10−3 which is a 3.0 [sigma] deviation from the background estimate. A log likelihood method is used to determine the most likely cross section as determined by the measured signal efficiencies, the expected backgrounds, and the observed data. Presented in Chapter 8 is a measurement of the cross section for p{bar p} → WZ + X at √s = 1.96 TeV. The WZ diboson production cross section is measured to be [sigma]{sub WZ} = 2.7{sub -1.3}{sup +1.7} pb. This is in agreement with the predicted Standard Model cross section.
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| Total Pages | : 7 |
| Release | : 2006 |
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The authors present the results of a search for W′ boson decaying to electron-neutrino pairs in p{bar p} collisions at a center-of-mass energy of 1.96 TeV, using a data sample corresponding to 205 pb−1 of integrated luminosity collected by the CDF II detector at Fermilab. They observe no evidence for this decay mode and set limits on the production cross section times branching fraction, assuming the neutrinos from W′ boson decays to be light. If they assume the manifest left-right symmetric model, they exclude a W′ boson with mass less than 788 GeV/c2 at the 95% confidence level.
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| Total Pages | : 12 |
| Release | : 1994 |
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Recent results from LEP experiments have substantially improved the knowledge of the Z boson. However, hadron colliders remain the only source of direct measurements of the W boson. There have been measurements of the W boson mass from the UA2 and CDF collaborations. The W mass continues to be a subject of great interest in testing the Standard Model. Here, the authors have made a preliminary determination of the W boson mass M{sub W} = 80.38 ± 0.23 GeV/c2 from a combined analysis of W → e[nu] and W → [mu][nu] in {anti p}p collisions at √s = 1.8 TeV. The electron data alone yields M{sub W} = 80.47 ± 0.15(stat.) ± 0.25(syst.) GeV/c2, while the muon data gives M{sub W} = 80.29 ± 0.20(stat.) ± 0.24(syst.) GeV/c2.
| Author | : Simone Marzani |
| Publisher | : Springer |
| Total Pages | : 205 |
| Release | : 2019-05-11 |
| Genre | : Science |
| ISBN | : 3030157091 |
This concise primer reviews the latest developments in the field of jets. Jets are collinear sprays of hadrons produced in very high-energy collisions, e.g. at the LHC or at a future hadron collider. They are essential to and ubiquitous in experimental analyses, making their study crucial. At present LHC energies and beyond, massive particles around the electroweak scale are frequently produced with transverse momenta that are much larger than their mass, i.e., boosted. The decay products of such boosted massive objects tend to occupy only a relatively small and confined area of the detector and are observed as a single jet. Jets hence arise from many different sources and it is important to be able to distinguish the rare events with boosted resonances from the large backgrounds originating from Quantum Chromodynamics (QCD). This requires familiarity with the internal properties of jets, such as their different radiation patterns, a field broadly known as jet substructure. This set of notes begins by providing a phenomenological motivation, explaining why the study of jets and their substructure is of particular importance for the current and future program of the LHC, followed by a brief but insightful introduction to QCD and to hadron-collider phenomenology. The next section introduces jets as complex objects constructed from a sequential recombination algorithm. In this context some experimental aspects are also reviewed. Since jet substructure calculations are multi-scale problems that call for all-order treatments (resummations), the bases of such calculations are discussed for simple jet quantities. With these QCD and jet physics ingredients in hand, readers can then dig into jet substructure itself. Accordingly, these notes first highlight the main concepts behind substructure techniques and introduce a list of the main jet substructure tools that have been used over the past decade. Analytic calculations are then provided for several families of tools, the goal being to identify their key characteristics. In closing, the book provides an overview of LHC searches and measurements where jet substructure techniques are used, reviews the main take-home messages, and outlines future perspectives.
