Combination of Tevatron Searches for the Standard Model Higgs Boson in the W+W- Decay Mode

Combination of Tevatron Searches for the Standard Model Higgs Boson in the W+W- Decay Mode
Author:
Publisher:
Total Pages: 11
Release: 2010
Genre:
ISBN:

We combine searches by the CDF and D0 collaborations for a Higgs boson decaying to W+W−. The data correspond to an integrated total luminosity of 4.8 (CDF) and 5.4 (D0) fb−1 of p{bar p} collisions at √s = 1.96 TeV at the Fermilab Tevatron collider. No excess is observed above background expectation, and resulting limits on Higgs boson production exclude a standard-model Higgs boson in the mass range 162-166 GeV at the 95% C.L.

Search for the Standard Model Higgs Boson in the Decay Mode H-] WW-] Lnulnu

Search for the Standard Model Higgs Boson in the Decay Mode H-] WW-] Lnulnu
Author:
Publisher:
Total Pages: 196
Release: 2009
Genre:
ISBN:

The question of the nature and principles of the universe and our place in it is the driving force of science since Mesopotamian astronomers glanced for the first time at the starry sky and Greek atomism has been formulated. During the last hundred years modern science was able to extend its knowledge tremendously, answering many questions, opening entirely new fields but as well raising many new questions. Particularly Astronomy, Astroparticle Physics and Particle Physics lead the race to answer these fundamental and ancient questions experimentally. Today it is known that matter consists of fermions, the quarks and leptons. Four fundamental forces are acting between these particles, the electromagnetic, the strong, the weak and the gravitational force. These forces are mediated by particles called bosons. Our confirmed knowledge of particle physics is based on these particles and the theory describing their dynamics, the Standard Model of Particles. Many experimental measurements show an excellent agreement between observation and theory but the origin of the particle masses and therefore the electroweak symmetry breaking remains unexplained. The mechanism proposed to solve this issue involves the introduction of a complex doublet of scalar fields which generates the masses of elementary particles via their mutual interactions. This Higgs mechanism also gives rise to a single neutral scalar boson with an unpredicted mass, the Higgs boson. During the last twenty years several experiments have searched for the Higgs boson but so far it escaped direct observation. Nevertheless these studies allow to further constrain its mass range. The last experimental limits on the Higgs mass have been set in 2001 at the LEP collider, an electron positron machine close to Geneva, Switzerland. The lower limit set on the Higgs boson mass is m{sub H}> 114.4 GeV/c2 and remained for many years the last experimental constraint on the Standard Model Higgs Boson due to the shutdown of the LEP collider and the experimental challenges at hadron machines as the Tevatron. This thesis was performed using data from the D0 detector located at the Fermi National Accelerator Laboratory in Batavia, IL. Final states containing two electrons or a muon and a tau in combination with missing transverse energy were studied to search for the Standard Model Higgs boson, utilizing up to 4.2 fb−1 of integrated luminosity. In 2008 the CDF and D0 experiments in a combined effort were able to reach for the first time at a hadron collider the sensitivity to further constrain the possible Standard Model Higgs boson mass range. The research conducted for this thesis played a pivotal role in this effort. Improved methods for lepton identification, background separation, assessment of systematic uncertainties and new decay channels have been studied, developed and utilized. Along with similar efforts at the CDF experiment these improvements led finally the important result of excluding the presence of a Standard Model Higgs boson in a mass range of m{sub H} = 160-170 GeV/c2 at 95% Confidence Level. Many of the challenges and methods found in the present analysis will probably in a similar way be ingredients of a Higgs boson evidence or discovery in the near future, either at the Tevatron or more likely at the soon starting Large Hadron Collider (LHC). Continuing to pursue the Higgs boson we are looking forward to many exciting results at the Tevatron and soon at the LHC. In Chapter 2 an introduction to the Standard Model of particle physics and the Higgs mechanism is given, followed by a brief outline of existing theoretical and experimental constraints on the Higgs boson mass before summarizing the Higgs boson production modes. Chapter 3 gives an overview of the experimental setup. This is followed by a description of the reconstruction of the objects produced in proton-antiproton collisions in Chapter 4 and the necessary calorimeter calibrations in Chapter 5. Chapter 6 follows with an explanation of the phenomenology of the proton-antiproton collisions and the data samples used. In Chapter 7 the search for the Standard Model Higgs boson using a di-electron final state is discussed, followed by the analysis of the final states using muons and hadronic decaying taus in Chapter 8. Finally a short outlook for the prospects of Higgs boson searches is given in Chapter 9.

Search for the Standard Model Higgs Boson in the Decay Mode H{u2192} W+W-{u2192} L+vl-v

Search for the Standard Model Higgs Boson in the Decay Mode H{u2192} W+W-{u2192} L+vl-v
Author:
Publisher:
Total Pages: 196
Release: 2009
Genre:
ISBN:

The question of the nature and principles of the universe and our place in it is the driving force of science since Mesopotamian astronomers glanced for the first time at the starry sky and Greek atomism has been formulated. During the last hundred years modern science was able to extend its knowledge tremendously, answering many questions, opening entirely new fields but as well raising many new questions. Particularly Astronomy, Astroparticle Physics and Particle Physics lead the race to answer these fundamental and ancient questions experimentally. Today it is known that matter consists of fermions, the quarks and leptons. Four fundamental forces are acting between these particles, the electromagnetic, the strong, the weak and the gravitational force. These forces are mediated by particles called bosons. Our confirmed knowledge of particle physics is based on these particles and the theory describing their dynamics, the Standard Model of Particles. Many experimental measurements show an excellent agreement between observation and theory but the origin of the particle masses and therefore the electroweak symmetry breaking remains unexplained. The mechanism proposed to solve this issue involves the introduction of a complex doublet of scalar fields which generates the masses of elementary particles via their mutual interactions. This Higgs mechanism also gives rise to a single neutral scalar boson with an unpredicted mass, the Higgs boson. During the last twenty years several experiments have searched for the Higgs boson but so far it escaped direct observation. Nevertheless these studies allow to further constrain its mass range. The last experimental limits on the Higgs mass have been set in 2001 at the LEP collider, an electron positron machine close to Geneva, Switzerland. The lower limit set on the Higgs boson mass is mH > 114.4 GeV/c2 and remained for many years the last experimental constraint on the Standard Model Higgs Boson due to the shutdown of the LEP collider and the experimental challenges at hadron machines as the Tevatron. This thesis was performed using data from the D0 detector located at the Fermi National Accelerator Laboratory in Batavia, IL. Final states containing two electrons or a muon and a tau in combination with missing transverse energy were studied to search for the Standard Model Higgs boson, utilizing up to 4.2 fb-1 of integrated luminosity. In 2008 the CDF and D0 experiments in a combined effort were able to reach for the first time at a hadron collider the sensitivity to further constrain the possible Standard Model Higgs boson mass range. The research conducted for this thesis played a pivotal role in this effort. Improved methods for lepton identification, background separation, assessment of systematic uncertainties and new decay channels have been studied, developed and utilized. Along with similar efforts at the CDF experiment these improvements led finally the important result of excluding the presence of a Standard Model Higgs boson in a mass range of mH = 160-170 GeV/c2 at 95% Confidence Level. Many of the challenges and methods found in the present analysis will probably in a similar way be ingredients of a Higgs boson evidence or discovery in the near future, either at the Tevatron or more likely at the soon starting Large Hadron Collider (LHC). Continuing to pursue the Higgs boson we are looking forward to many exciting results at the Tevatron and soon at the LHC. In Chapter 2 an introduction to the Standard Model of particle physics and the Higgs mechanism is given, followed by a brief outline of existing theoretical and experimental constraints on the Higgs boson mass before summarizing the Higgs boson production modes. Chapter 3 gives an overview of the experimental setup. This is followed by a description of the reconstruction of the objects produced in proton-antiproton collisions in Chapter 4 and the necessary calorim...

Discovery Of The Higgs Boson

Discovery Of The Higgs Boson
Author: Aleandro Nisati
Publisher: World Scientific
Total Pages: 470
Release: 2016-08-26
Genre: Science
ISBN: 981442546X

The recent observation of the Higgs boson has been hailed as the scientific discovery of the century and led to the 2013 Nobel Prize in physics. This book describes the detailed science behind the decades-long search for this elusive particle at the Large Electron Positron Collider at CERN and at the Tevatron at Fermilab and its subsequent discovery and characterization at the Large Hadron Collider at CERN. Written by physicists who played leading roles in this epic search and discovery, this book is an authoritative and pedagogical exposition of the portrait of the Higgs boson that has emerged from a large number of experimental measurements. As the first of its kind, this book should be of interest to graduate students and researchers in particle physics.

Observation of a New State in the Search for the Higgs Boson at CMS

Observation of a New State in the Search for the Higgs Boson at CMS
Author: Giovanni Petrucciani
Publisher: Springer
Total Pages: 232
Release: 2014-12-04
Genre: Science
ISBN: 8876424822

This book describes the searches that lead to the discovery of a Higgs boson performed at CMS, one of the two main experiments at the CERN LHC. After an overview of the theory and of the CMS experiment, all search channels are described, with emphasis on the ones with the best sensitivity. The statistical methodology used to analyse and the outcomes of the searches and the discovery results are then presented in detail.

Search for the Standard Model Higgs Boson in ZH 2![mu]+[mu]-b$\bar{b}$ Production at DØ and Evidence for the H2!b$\bar{b}$ Decay at the Tevatron

Search for the Standard Model Higgs Boson in ZH 2![mu]+[mu]-b$\bar{b}$ Production at DØ and Evidence for the H2!b$\bar{b}$ Decay at the Tevatron
Author:
Publisher:
Total Pages: 176
Release: 2014
Genre:
ISBN:

Search for ZH → [mu]+[mu]-b$\bar{b}$ is presented, using a Run 2 dataset with an integrated luminosity of 9.7 fb-1 collected by the DØ detector. Selected events contain at least two reconstructed jets and a Z candidate reconstructed with two opposite-sign charged muons. Random forests of decision trees are trained to distinguish between signal and background events in two orthogonal b-tag samples. The ZH → [mu]+[mu]-b$\bar{b}$b analysis is then combined with ZH → e+e-b$\bar{b}$ analysis. For the combined results of ZH → l+l-b$\bar{b}$b, no Higgs signal is observed, limits are set on the ZH cross-section BR(H→ b$\bar{b}$) for different Higgs masses, from 90 to 150 GeV. For a Standard Model (SM) Higgs boson of mass 125 GeV, the observed cross-section limit is 7.1 times the SM cross-section with an expected sensitivity of 5.1 times the SM cross section. The result of ZH → l+l-b$\bar{b}$b channel has been combined with searches in other Higgs decay channels at the Tevatron, which led to the first evidence of H → b$\bar{b}$.

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 DØ Experiment

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 DØ Experiment
Author:
Publisher:
Total Pages: 176
Release: 2010
Genre:
ISBN:

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.

Higgs Boson Studies at the Tevatron

Higgs Boson Studies at the Tevatron
Author:
Publisher:
Total Pages: 5
Release: 2016
Genre:
ISBN:

We present the combination of searches for the Standard Model Higgs boson at a center-of-mass energy of √s = 1.96 TeV , using the full Run 2 dataset collected with the CDF and D0 detectors at the Fermilab Tevatron collider. We also present combined measurements of Higgs Boson production cross sections, branching ratios, and couplings to fermions and bosons. Lastly, we present tests of different spin and parity hypotheses for a particle H of mass 125 GeV produced in association with a vector boson and decaying into a pair of b quarks, and place constraints on such hypotheses using the D0 data.

Combined CDF and D0 Searches for the Standard Model Higgs Boson Decaying to Two Photons with Up to 8.2 Fb^-1

Combined CDF and D0 Searches for the Standard Model Higgs Boson Decaying to Two Photons with Up to 8.2 Fb^-1
Author:
Publisher:
Total Pages: 11
Release: 2011
Genre:
ISBN:

We combine results from CDF and D0's direct searches for the standard model (SM) Higgs boson (H) produced in p{bar p} collisions at the Fermilab Tevatron at √s = 1.96 TeV, focusing on the decay H → [gamma][gamma]. We compute upper limits on the Higgs boson production cross section times the decay branching fraction in the range 100