Search For Standard Model Higgs Boson Production In Association With A W Boson Using A Matrix Element Technique At Cdf In P Bar P Collisions At Sqrt S
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Search For Standard Model Higgs Boson Production In Association With A W Boson Using A Matrix Element Technique At Cdf In P Bar P Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2011
Search For Standard Model Higgs Boson Production In Association With A W Boson Using A Matrix Element Technique At Cdf In P Bar P Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
This paper presents a search for standard model Higgs boson production in association with a W boson using events recorded by the CDF experiment in a dataset corresponding to an integrated luminosity of 5.6 fb−1. The search is performed using a matrix element technique in which the signal and background hypotheses are used to create a powerful discriminator. The discriminant output distributions for signal and background are fit to the observed events using a binned likelihood approach to search for the Higgs boson signal. We find no evidence for a Higgs boson, and 95% confidence level (C.L.) upper limits are set on?(p{bar p} → WH) x?(H → b{bar b}). The observed limits range from 3.5 to 37.6 relative to the standard model expectation for Higgs boson masses between m{sub H} = 100 GeV/c2 and m{sub H} = 150 GeV/c2. The 95% C.L. expected limit is estimated from the median of an ensemble of simulated experiments and varies between 2.9 and 32.7 relative to the production rate predicted by the standard model over the Higgs boson mass range studied.
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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language : en
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Release Date : 2010
Search For The Standard Model Higgs Boson Associated With A W Boson Using Matrix Element Technique In The Cdf Detector At The Tevatron written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
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 Standard Model Higgs Boson Produced In Association With A Z Boson In P Bar P Collisions At Sqrt S
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language : en
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Release Date : 2012
Search For The Standard Model Higgs Boson Produced In Association With A Z Boson In P Bar P Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
We present a search for the standard model Higgs boson produced in association with a Z boson, using up to 7.9 fb−1 of integrated luminosity from p{bar p} collisions collected with the CDF II detector. We utilize several novel techniques, including multivariate lepton selection, multivariate trigger parametrization, and a multi-stage signal discriminant consisting of specialized functions trained to distinguish individual backgrounds. By increasing acceptance and enhancing signal discrimination, these techniques have significantly improved the sensitivity of the analysis above what was expected from a larger dataset alone. We observe no significant evidence for a signal, and we set limits on the ZH production cross section. For a Higgs boson with mass 115 GeV/c2, we expect (observe) a limit of 3.9 (4.8) times the standard model predicted value, at the 95% credibility level.
Search For Standard Model Higgs Boson Production In Association With A W Boson At Cdf
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language : en
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Release Date : 2008
Search For Standard Model Higgs Boson Production In Association With A W Boson At Cdf written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
We present a search for standard model Higgs boson production in association with a W boson in proton-antiproton collisions (p{bar p} → W{sup {+-}}H → l[nu]b{bar b}) at a center of mass energy of 1.96 TeV. The search employs data collected with the CDF II detector which correspond to an integrated luminosity of approximately 1 fb−1. We select events consistent with a signature of a single lepton (e{sup {+-}}/[mu]{sup {+-}}), missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with a secondary vertex tagging method and a neural network filter technique. The observed number of events and the dijet mass distributions are consistent with the standard model background expectations, and we set 95% confidence level upper limits on the production cross section times branching ratio ranging from 3.9 to 1.3 pb for Higgs boson masses from 110 to 150 GeV/c2, respectively.
A Search For The Standard Model Higgs Boson Produced In Association With A W Boson
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Author :
language : en
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Release Date : 2011
A Search For The Standard Model Higgs Boson Produced In Association With A W Boson written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
We present a search for a standard model Higgs boson produced in association with a W boson using data collected with the CDF II detector from p{bar p} collisions at √s = 1.96 TeV. The search is performed in the WH → l[nu]b{bar b} channel. The two quarks usually fragment into two jets, but sometimes a third jet can be produced via gluon radiation, so we have increased the standard two-jet sample by including events that contain three jets. We reconstruct the Higgs boson using two or three jets depending on the kinematics of the event. We find an improvement in our search sensitivity using the larger sample together with this multijet reconstruction technique. Our data show no evidence of a Higgs boson, so we set 95% confidence level upper limits on the WH production rate. We set limits between 3.36 and 28.7 times the standard model prediction for Higgs boson masses ranging from 100 to 150 GeV/c2.
A Search For The Higgs Boson Produced In Association With Z To Ell Ell Using The Matrix Element Method At Cdf Ii
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language : en
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Release Date : 2009
A Search For The Higgs Boson Produced In Association With Z To Ell Ell Using The Matrix Element Method At Cdf Ii written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
We present a search for associated production of the standard model (SM) Higgs boson and a Z boson where the Z boson decays to two leptons and the Higgs decays to a pair of b quarks in p{bar p} collisions at the Fermilab Tevatron. We use event probabilities based on SM matrix elements to construct a likelihood function of the Higgs content of the data sample. In a CDF data sample corresponding to an integrated luminosity of 2.7 fb−1 we see no evidence of a Higgs boson with a mass between 100 GeV/c2 and 150 GeV/c2. We set 95% confidence level (C.L.) upper limits on the cross-section for ZH production as a function of the Higgs boson mass m{sub H}; the limit is 8.2 times the SM prediction at m{sub H} = 115 GeV/c2.
Search For The Higgs Boson Produced In Association With A W Boson At Cdf Run Ii
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language : en
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Release Date : 2009
Search For The Higgs Boson Produced In Association With A W Boson At Cdf Run Ii written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
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 Standard Model Higgs Boson Production In Association With A W Boson Using A Neural Network
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Author :
language : en
Publisher:
Release Date : 2009
Search For Standard Model Higgs Boson Production In Association With A W Boson Using A Neural Network written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
We present a search for standard model Higgs boson production in association with a W boson in proton-antiproton collisions (p{bar p} → W{sup {+-}}H → l[nu]b{bar b}) at a center of mass energy of 1.96 TeV. The search employs data collected with the CDF II detector that correspond to an integrated luminosity of approximately 1.9 fb−1. We select events consistent with a signature of a single charged lepton (e{sup {+-}}/[mu]{sup {+-}}), missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with a secondary vertex tagging method, a jet probability tagging method, and a neural network filter. We use kinematic information in an artificial neural network to improve discrimination between signal and background compared to previous analyses. The observed number of events and the neural network output distributions are consistent with the standard model background expectations, and we set 95% confidence level upper limits on the production cross section times branching fraction ranging from 1.2 to 1.1 pb or 7.5 to 102 times the standard model expectation for Higgs boson masses from 110 to 150 GeV/c2, respectively.
Combined Cdf And D0 Upper Limits On Standard Model Higgs Boson Production With Up To 6 7 Fb 1 Of Data
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language : en
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Release Date : 2010
Combined Cdf And D0 Upper Limits On Standard Model Higgs Boson Production With Up To 6 7 Fb 1 Of Data written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
We combine results from CDF and D0 on direct searches for the standard model (SM) Higgs boson (H) in p{bar p} collisions at the Fermilab Tevatron at (square root)s = 1.96 TeV. Compared to the previous Tevatron Higgs search combination more data have been added, additional new channels have been incorporated, and some previously used channels have been reanalyzed to gain sensitivity. We use the latest parton distribution functions and gg --> H theoretical cross sections when comparing our limits to the SM predictions. With up to 5.9 fb−1 of data analyzed at CDF, and up to 6.7 fb−1 at D0, the 95% C.L. upper limits on Higgs boson production are factors of 1.56 and 0.68 the values of the SM cross section for a Higgs boson mass of m{sub H} = 115 GeV/c2 and 165 GeV/c2. We exclude, at the 95% C.L., a new and larger region at high mass between 158
A Search For The Higgs Boson Using Neural Networks In Events With Missing Energy And Boldit B Quark Jets In P Bar P Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2009
A Search For The Higgs Boson Using Neural Networks In Events With Missing Energy And Boldit B Quark Jets In P Bar P Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
We report on a search for the standard model Higgs boson produced in association with a W or Z boson in p{bar p} collisions at (square root)s = 1.96 TeV recorded by the CDF II experiment at the Tevatron in a data sample corresponding to an integrated luminosity of 2.1 fb−1. We consider events which have no identified charged leptons, an imbalance in transverse momentum, and two or three jets where at least one jet is consistent with originating from the decay of a b hadron. We find good agreement between data and predictions. We place 95% confidence level upper limits on the production cross section for several Higgs boson masses ranging from 110 GeV/c2 to 150 GeV/c2. For a mass of 115 GeV/c2 the observed (expected) limit is 6.9 (5.6) times the standard model prediction.