Search for a Standard Model Higgs Boson in the Channel $VH\to VWW$ with Leptons and Hadronic $\tau$ in the Full CDF Run II Data Set

Search for a Standard Model Higgs Boson in the Channel $VH\to VWW$ with Leptons and Hadronic $\tau$ in the Full CDF Run II Data Set
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Total Pages: 106
Release: 2015
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We present the results of the CDF search for a Standard Model Higgs boson decaying into a pair of W bosons with electrons, muons and hadronically decaying taus in the final state. In particular, we investigate a channel with three objects, two leptons and a tau. In 9.7 fb-1 of data we expect 40.0 ± 5.4 background events and 0.54 ± 0.05 signal events for a Higgs mass hypothesis of 160 GeV/c2, whereas in data we count 28 events. We set a 95% C.L. upper limit on [sigma]/[sigma]SM of 12.6 for a Higgs mass hypothesis of 160 GeV/c2. The expected 95% C.L. upper limit for the same mass is 12.4. Results for other ninete 0 GeV/c2 to 200 GeV/c2 are also presented.

Beyond the Standard Model Higgs Boson Searches at the Tevatron

Beyond the Standard Model Higgs Boson Searches at the Tevatron
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Total Pages: 7
Release: 2010
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The search for the Higgs boson is one of the main goals in High Energy Physics and one of the highest priorities at Run II of the Tevatron. There are many alternative Higgs boson models beyond the SM, including Supersymmetry (SUSY) and Fermiophobic Higgs bosons, which can actively be probed at the Tevatron, and in the absence of an excess constrained. The latest limits for several SUSY searches are presented in Section 2 and for the Fermiophobic Higgs boson searches in Section 3. More information on all these searches, along with the latest results, can be found on the CDF and D0 public results webpages. Results are presented for beyond the Standard Model Higgs boson searches using up to 4.2 fb−1 of data from Run II at the Tevatron. No significant excess is observed in any of the channels so 95% confidence level limits are presented.

A Search for the Standard Model Higgs Boson in CDF II Data

A Search for the Standard Model Higgs Boson in CDF II Data
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Total Pages: 141
Release: 2012
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This dissertation presents a search for the standard model Higgs boson in the associated production process p $\bar{p}$ → ZH → e+e-b$\bar{b}$. Data amounting to an integrated luminosity of 7.5 fb-1 at √s = 1.96 TeV collected at the Collider Detector at Fermilab (CDF) at the Tevatron are analyzed. Two objectives are pursued in the methods applied: maximize acceptance, and distinguish the signal from background. The first aim is met by applying a neural-network-based electron identi cation and considering multiple electron triggers in an effort to improve Z acceptance. In an attempt to maximize the Higgs acceptance, three b quark identification schemes are used allowing for varying event conditions. The latter goal is met by employing more multivariate techniques. First, the dijet mass resolution is improved by a neural network. Then, both single variables and boosted decision tree outputs are fed into a segmented final discriminant simultaneously isolating the signal-like events from the Z with additional jets background and the kinematically di erent tt background. Good agreement is seen with the null hypothesis and upper production cross section ( ZH) times branching ratio (BR(H →b $\bar{b}$)) limits are set for 11 mass hypotheses between 100 and 150 GeV/c2 at the 95% confidence level. For a Higgs boson mass of 115 GeV/c2, this channel sets an observed (expected) upper limit of 3.9 (5.8) times the standard model value of ZH BR(H → b $\bar{b}$). The inclusion of this channel within the combined CDF and Tevatron limits is discussed.

Higgs Searches and Prospects at CDF.

Higgs Searches and Prospects at CDF.
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Release: 2003
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The Standard model of electroweak interactions (SM) has been extremely successful in describing interactions of elementary particles over the last decades. The Higgs scalar boson is one of the key elements of the SM: Higgs interactions with the other particles generate the particle masses and allow to keep the theory renormalizable at electroweak scale. All the particles predicted by the SM but the Higgs boson have already been observed experimentally and therefore search for the Higgs is one of the most important scientific goals for high energy physics. The current lower limit on the SM Higgs mass M{sub H}> 114.4 GeV at 95% CL has been established by LEP experiments. In this paper we review CDF Run I results on Higgs searches including the Higgs bosons predicted by the minimal supersymmetric extention of the Standard Model (MSSM) and discuss the Run II prospects.

Search for the Standard Model Higgs Boson Associated with a W Boson Using Matrix Element Technique in the CDF Detector at the Tevatron

Search for the Standard Model Higgs Boson Associated with a W Boson Using Matrix Element Technique in the CDF Detector at the Tevatron
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Total Pages: 195
Release: 2010
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In this thesis a direct search for the Standard Model Higgs boson production in association with a W boson at the CDF detector in the Tevatron is presented. This search contributes predominantly in the region of low mass Higgs region, when the mass of Higgs boson is less than about 135 GeV. The search is performed in a final state where the Higgs boson decays into two b quarks, and the W boson decays leptonically, to a charged lepton (it can be an electron or a muon) and a neutrino. This work is organized as follows. Chapter 2 gives an overview of the Standard Model theory of particle physics and presents the SM Higgs boson search results at LEP, and the Tevatron colliders, as well as the prospects for the SM Higgs boson searches at the LHC. The dataset used in this analysis corresponds to 4.8 fb−1 of integrated luminosity of p{bar p} collisions at a center of mass energy of 1.96 TeV. That is the luminosity acquired between the beginning of the CDF Run II experiment, February 2002, and May 2009. The relevant aspects, for this analysis, of the Tevatron accelerator and the CDF detector are shown in Chapter 3. In Chapter 4 the particles and observables that make up the WH final state, electrons, muons, E{sub T}, and jets are presented. The CDF standard b-tagging algorithms to identify b jets, and the neural network flavor separator to distinguish them from other flavor jets are also described in Chapter 4. The main background contributions are those coming from heavy flavor production processes, such as those coming from Wbb, Wcc or Wc and tt. The signal and background signatures are discussed in Chapter 5 together with the Monte CArlo generators that have been used to simulate almost all the events used in this thesis. WH candidate events have a high-p{sub T} lepton (electron or muon), high missing transverse energy, and two or more than two jets in the final state. Chapter 6 describes the event selection applied in this analysis and the method used to estimate the background contribution. The Matrix Element method, that was successfully used in the single t0p discovery analysis and many other analyses within the CDF collaboration, is the multivariate technique used in this thesis to discriminate signal from background events. With this technique is possible to calculate a probability for an event to be classified as signal or background. These probabilities are then combined into a discriminant function called the Event Probability Discriminant, EPD, which increases the sensitivity of the WH process. This method is described in detail in Chapter 7. As no evidence for the signal has been found, the results obtained with this work are presented in Chapter 8 in terms of exclusion regions as a function of the mass of the Higgs boso, taking into account the full systematics. The conclusions of this work to obtain the PhD are presnted in Chapter 9.

Search for the Higgs Boson Produced in Association with a W Boson at CDF Run II.

Search for the Higgs Boson Produced in Association with a W Boson at CDF Run II.
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Total Pages: 142
Release: 2009
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We present a search for standard model Higgs boson production in association with a W boson in proton-antiproton collisions (p{bar p} 2!W{sup {+-}}H 2!l[nu]b{bar b}) at a center of mass energy of 1.96 TeV. WH candidate events have a signature of a single lepton (E{sup {+-}}/[mu]{sup {+-}}), missing transverse energy, and two jets. The search looks for candidate events in approximately 2.7 fb−1 of data recorded with the CDF II detector. The high-p{sub T} lepton (e, [mu]) in the events provides a distinct signature for triggering and most of the events in the dataset come from high-p{sub t} lepton triggers. Our analysis improves on prior searches by including events recorded on the E{sub T} + 2 Jets trigger with a lepton reconstructed as an isolated high-p{sub T} charged particle. We increase the sample purity by identifying ('tagging') long-lived b-hadrons in jets. A neural network combines distinguishing kinematic information into a function optimized for WH sensitivity. The neural network output distributions are consistent with the standard model background expectations and we set limits upper limits on the rate of Higgs production. We set 95% confidence level upper limits on the WH production cross section times branching ratio for Higgs masses from 100 to 150 GeV/c2 and express our results as a ratio of the experimental limit to the theoretical Standard Model production rate. Our limits range from 3.6 (4.3 expected) to 61.1 (43.2 expected) for Higgs masses from 100 to 150 GeV/c2, respectively.

Search for the Higgs Boson in the All-Hadronic Final State Using the CDF II Detector

Search for the Higgs Boson in the All-Hadronic Final State Using the CDF II Detector
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Release: 2013
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This thesis reports the result of a search for the Standard Model Higgs boson in events containing four reconstructed jets associated with quarks. For masses below 135 GeV/c2, the Higgs boson decays to bottom-antibottom quark pairs are dominant and result primarily in two hadronic jets. An additional two jets can be produced in the hadronic decay of a W or Z boson produced in association with the Higgs boson, or from the incoming quarks that produced the Higgs boson through the vector boson fusion process. The search is performed using a sample of s = sqrt(1.96) TeV proton-antiproton collisions corresponding to an integrated luminosity of 9.45 fb-1 recorded by the CDF II detector. The data are in agreement with the background model and 95% credibility level upper limits on Higgs boson production are set as a function of the Higgs boson mass. The median expected (observed) limit for a 125 GeV/c2 Higgs boson is 11.0 (9.0) times the predicted standard model rate.