Search For The Standard Model Higgs Boson In The Wh U2192 V B Bar B Channel With The D0 Detector

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Search For The Standard Model Higgs Boson In The Wh U2192 V B Bar B Channel With The D0 Detector

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Author :
language : en
Publisher:
Release Date : 2009

Search For The Standard Model Higgs Boson In The Wh U2192 V B Bar B Channel With The D0 Detector 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.

A search for the Standard Model Higgs boson is performed in 4.0 fb-1 of p$ar{p}$ collisions at √s = 1.96 TeV, collected with the DØ detector at the Fermilab Tevatron. The final state considered is a pair of b-jets with large missing transverse energy and one hadronic tau decay as expected from the reaction p$ar{p}$ → WH → ? v b$ar{b}$. Boosted decision trees are used to discriminate the signal from the background. Good agreement is observed between data and expected backgrounds. For a Higgs boson mass of 115 GeV, a limit is set at 95% C.L. on the cross-section times branching fraction of (p$ar{p}$→ (Z/W)H)×(H → b$ar{b}$) which is 14 times larger than the Standard Model value.

Search For The Standard Model Higgs Boson In The Wh2 Tau V B Bar B Channel With The D0 Detector

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Author :
language : en
Publisher:
Release Date : 2009

Search For The Standard Model Higgs Boson In The Wh2 Tau V B Bar B Channel With The D0 Detector 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.

A search for the Standard Model Higgs boson is performed in 4.0 fb-1 of p$\bar{p}$ collisions at √s = 1.96 TeV, collected with the DØ detector at the Fermilab Tevatron. The final state considered is a pair of b-jets with large missing transverse energy and one hadronic tau decay as expected from the reaction p$\bar{p}$ → WH → [tau] v b$\bar{b}$. Boosted decision trees are used to discriminate the signal from the background. Good agreement is observed between data and expected backgrounds. For a Higgs boson mass of 115 GeV, a limit is set at 95% C.L. on the cross-section times branching fraction of (p$\bar{p}$→ (Z/W)H)×(H → b$\bar{b}$) which is 14 times larger than the Standard Model value.

First Search For The Standard Model Higgs Boson Using The Semileptonic Decay Channel

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language : en
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Release Date : 2010

First Search For The Standard Model Higgs Boson Using The Semileptonic Decay Channel 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.

This dissertation presents the first search for the standard model Higgs boson (H) in decay topologies containing a muon, an imbalance in transverse momentum (ET) and jets, using p$ar{p}$ collisions at √s = 1.96 TeV with an integrated luminosity of 4.3 fb-1 recorded with the D0 detector at the Fermilab Tevatron Collider. This analysis is sensitive primary to contributions from Higgs bosons produced through gluon fusion, with subsequent decay H → WW → ??jj where W represents a real or virtual W boson. In the absence of signal, limits are set at 95% confidence on the production and decay of the standard model Higgs boson for MH in the range of 115-200 GeV. For MH = 165 GeV, the observed and expected limits are factors of 11.2 larger than the standard model value. Combining this channel with e?jj final states and including earlier data to increase the integrated luminosity to 5.4 fb-1 produces observed(expected) limits of 5.5(3.8) times the standard model value.

Finding The Higgs Boson Of The Standard Model In The Channel Zh U2192 E E B Bar B With The D0 Detector At The Tevatron Recherche Du Boson De Higgs Du Nideke Standard Dans Le Canal Zh U2192 E E B Bar B Avec Le Detecteur D Aupres Du Tevatron

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language : en
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Release Date : 2010

Finding The Higgs Boson Of The Standard Model In The Channel Zh U2192 E E B Bar B With The D0 Detector At The Tevatron Recherche Du Boson De Higgs Du Nideke Standard Dans Le Canal Zh U2192 E E B Bar B Avec Le Detecteur D Aupres Du 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.

The organization of this thesis consists of three main ideas: the first presents the theoretical framework and experimental, as well as objects used in the analysis and the second relates to the various work tasks of service that I performed on the calorimeter, and the third is the search for the Higgs boson in the channel ZH → e+e-b$ar{b}$. Thus, this thesis has the following structure: Chapter 1 is an introduction to the standard model of particle physics and the Higgs mechanism; Chapter 2 is an overview of the complex and the acceleration of the Tevatron at Fermilab DØ detector; Chapter 3 is an introduction to physical objects used in this thesis; Chapter 4 presents the study made on correcting the energy measured in the calorimeter; Chapter 5 describes the study of certification of electrons in the calorimeter; Chapter 6 describes the study of certification of electrons in the intercryostat region of calorimeter; Chapter 7 Detailed analysis on the search for Higgs production in the channel ZH → e+e-b$ar{b}$; and Chapter 8 presents the final results of the calculations of upper limits to the production cross section of the Higgs boson on a range of low masses.

Search For A Light Higgs Boson In The Channel Wh U2192 E E B Bar B In P Bar P Collision With Sqrt S

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language : en
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Release Date : 2005

Search For A Light Higgs Boson In The Channel Wh U2192 E E B Bar B In P Bar P Collision With 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 2005 with categories.

Although the standard model of particle physics has been very successfull in describing nature it needs to be extended by the Higgs mechanism to explain the particle masses observed in experiments. This mechanism introduces a new elementary particle called the Higgs boson. Current research at particle accelerators focuses on the search for the Higgs boson as a major goal. This analysis uses the data recorded with the D0-detector of the Tevatron at the Fermi National Accelerator Laboratory (FNAL). The Tevatron collides protons and antiprotons at a center of mass energy of √s=1.96 TeV. The primary goal of the analysis was the search for a light Higgs boson in the WH channel. For this the process pp→ WH → ev bb was used. Furthermore a measurement of the Wbb production cross section has been performed. For the measurements a total intagrated luminosity of L=255pb-1 was available. For the selection of the desired processes events with electrons, missing transverse momentum and at least two jets have been used. At least two of the jets were required to be identified as b-jets. To obtain an efficient event selection many event properties had to be calculated and methods to cut on them needed to be optimized. Based on the selected events the Wbb production cross section has been calculated. After includinng the branching ratio BR(W→ev)=0.108 the result is ?(Wbb)=21.8 pb (+15.5; -20.0 pb(sys+stat)) for events where the b-quarks satisfy p_T>8 GeV und.

Search For The Standard Model Higgs Boson In Zh U2192 V Bar V B Bar B Channel In P Bar P Collisions At U221a S

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Author :
language : en
Publisher:
Release Date : 2011

Search For The Standard Model Higgs Boson In Zh U2192 V Bar V B Bar B Channel In P Bar P Collisions At U221a 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.

A search for the standard model Higgs boson is performed in 5.2 fb-1 of p$ar{p}$ collisions at p √s = 1.96 TeV, collected with the DØ detector at the Fermilab Tevatron. The final state considered is a pair of b jets with large missing transverse energy, as expected from p$ar{p}$→ ZH → v$ar{v}$b$ar{b}$ production. The search is also sensitive to the WH → lvb$ar{b}$ channel, where the charged lepton is not identified. Boosted decision trees are used to discriminate signal from background. Good agreement is observed between data and expected backgrounds, and, for a Higgs-boson mass of 115 GeV, a limit is set at 95% C.L. on the cross section multiplied by branching fraction of (p$ar{p}$ → (Z/W)H) × (H → b$ar{b}$) that is a factor 4.57 expected and 3.73 observed larger than the value expected from the standard model.

Search For The Higgs Boson In The Zh U2192 V Bar V B Bar B Channel

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Author :
language : en
Publisher:
Release Date : 2010

Search For The Higgs Boson In The Zh U2192 V Bar V B Bar B Channel 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 the Standard Model of particle physics, the Higgs boson generates elementary particle masses. Current theoretical and experimental constraints lead to a Higgs boson mass between 114.4 and 158 GeV with 95% confidence level. Moreover, Tevatron has recently excluded the mass ranges between 100 and 109 GeV, 158 and 175 GeV with 95% confidence level. These results gives a clear indication to search for a Higgs boson at low mass. The D0 detector is located near Chicago, at the Tevatron, a proton-antiproton collider with an energy in the center of mass of 1.96 TeV. The topic of this thesis is the search for a Higgs boson in association with a Z boson. This channel is sensitive to low mass Higgs boson (135 GeV) which has a branching ratio H → bb varies between 50% and 90% in this mass range. The decay channel ZH → v$ar{v}$b$ar{b}$ studied has in the final state 2 heavy-flavor jets and some missing transverse energy due to escaping neutrinos. The heavy-flavor jets identification ('b-tagging') is done with a new algorithm (SLTNN) developed specifically for semi-leptonic decay of b quarks. The Higgs boson search analysis was performed with 3 fbsup-1

Search For The Standard Model Higgs Boson In The Zh Vvbb Channel In 5 2 Fb 1 Of P Pbar Collisions At Sqrt S

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language : en
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Release Date : 2009

Search For The Standard Model Higgs Boson In The Zh Vvbb Channel In 5 2 Fb 1 Of P Pbar 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.

A search is performed for the standard model Higgs boson in 5.2 fb−1 of p{bar p} collisions at √s = 1.96 TeV, collected with the D0 detector at the Fermilab Tevatron Collider. The final state considered is a pair of b jets and large missing transverse energy, as expected from p{bar p} → ZH → [nu]{bar [nu]}b{bar b} production. The search is also sensitive to the WH → l{nu}b{bar b} channel when the charged lepton is not identified. For a Higgs boson mass of 115 GeV, a limit is set at the 95% C.L. on the cross section multiplied by branching fraction for (p{bar p} → (Z/W)H) x (H → b{bar b}) that is a factor of 3.7 larger than the standard model value, consistent with the factor of 4.6 expected.

Search For The Standard Model Higgs Boson In P Bar P Interactions With The Decay Mode H U2192 W W U2192 V V At The D Experiment

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Author :
language : en
Publisher:
Release Date : 2010

Search For The Standard Model Higgs Boson In P Bar P Interactions With The Decay Mode H U2192 W W U2192 V V At The D Experiment 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.

A search for the standard model Higgs boson in p$ar{p}$ collisions resulting in two muons and large missing transverse energy is presented. The analysis uses 4.2 fb-1 of integrated luminosity at a center-of-mass energy of √s = 1.96 TeV collected between April 2002 and December 2008 with the D0 detector at the Fermilab Tevatron collider. No significant excess above the background estimation is observed and limits are derived on Higgs boson production.

A Search For The Standard Model Higgs Boson In The Process Zh U2192 L L B Bar B In 4 1 Fb 1 Of Cdf Ii Data

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Author :
language : en
Publisher:
Release Date : 2010

A Search For The Standard Model Higgs Boson In The Process Zh U2192 L L B Bar B In 4 1 Fb 1 Of Cdf Ii 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.

The standard model of particle physics provides a detailed description of a universe in which all matter is composed of a small number of fundamental particles, which interact through the exchange of force - carrying gauge bosons (the photon, W ±, Z and gluons). The organization of the matter and energy in this universe is determined by the effects of three forces; the strong, weak, and electromagnetic. The weak and electromagnetic forces are the low energy manifestations of a single electro-weak force, while the strong force binds quarks into protons and neutrons. The standard model does not include gravity, as the effect of this force on fundamental particles is negligible. Four decades of experimental tests, spanning energies from a few electron-volts (eV) up to nearly two TeV, confirm that the universe described by the standard model is a reasonable approximation of our world. For example, experiments have confirmed the existence of the top quark, the W± and the Z bosons, as predicted by the standard model. The latest experimental averages for the masses of the top quark, W± and Z are respectively 173.1 ± 0.6(stat.) ± 1.1(syst.), 80.399 ± 0.023 and 91.1876 ± 0.0021 GeV/c2. The SM is a gauge field theory of zero mass particles. However, the SM is able to accommodate particles with non-zero mass through the introduction of a theoretical Higgs field which permeates all of space. Fermions gain mass through interactions with this field, while the longitudinal components of the massive W± and Z are the physical manifestations of the field itself. Introduction of the Higgs field, directly leads to the predicted existence of an additional particle, the Higgs boson. The Higgs boson is the only particle of the standard model that has not been observed, and is the only unconfirmed prediction of the theory. The standard model describes the properties of the Higgs boson in terms of its mass, which is a free parameter in the theory. Experimental evidence suggests that the Higgs mass has a value between 114.4 and 186 GeV/c2. Particles with a mass in this range can be produced in collisions of less massive particles accelerated to near the speed of light. Currently, one of only a few machines capable of achieving collision energies large enough to potentially produce a standard model Higgs boson is the Tevatron proton-antiproton collider located at Fermi National Accelerator Laboratory in Batavia, Illinois. This dissertation describes the effort to observe the standard model Higgs in Tevatron collisions recorded by the Collider Detector at Fermilab (CDF) II experiment in the ZH →l+l-b$ar{b}$ production and decay channel. In this process, the Higgs is produced along with a Z boson which decays to a pair of electrons or muons (Z →l+l-), while the Higgs decays to a bottom anti-bottom quark pair (H → b$ar{b}$). A brief overview of the standard model and Higgs theory is presented in Chapter 2. Chapter 3 explores previous searches for the standard model Higgs at the Tevatron and elsewhere. The search presented in this dissertation expands upon the techniques and methods developed in previous searches. The fourth chapter contains a description of the Tevatron collider and the CDF II detector. The scope of the discussion in Chapter 4 is limited to the experimental components relevant to the current ZH →l+l-b$ar{b}$ search. Chapter 5 presents the details of object reconstruction; the methods used to convert detector signals into potential electrons, muons or quarks. Chapter six describes the data sample studied for the presence of a ZH →l+l-b$ar{b}$ signal and details the techniques used to model the data. The model accounts for both signal and non-signal processes (backgrounds) which are expected to contribute to the observed event sample. Chapters 7 and 8 summarize the event selectio...