Search For The Standard Model Higgs Boson Produced Through Vector Boson Fusion And Decaying To Mathrm B Bar B
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Search For The Standard Model Higgs Boson Produced Through Vector Boson Fusion And Decaying To Mathrm B Bar B
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Author :
language : en
Publisher:
Release Date : 2015
Search For The Standard Model Higgs Boson Produced Through Vector Boson Fusion And Decaying To Mathrm B Bar B written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
A first search is reported for a standard model Higgs boson (H) that is produced through vector boson fusion and decays to a bottom-quark pair. Two data samples, corresponding to integrated luminosities of 19.8 fb-1 and 18.3 fb-1 of proton-proton collisions at √s=8 TeV were selected for this channel at the CERN LHC. The observed significance in these data samples for a H→$mathrm{bar{b}}$ signal at a mass of 125 GeV is 2.2 standard deviations, while the expected significance is 0.8 standard deviations. The fitted signal strength ?=?/?SM=2.8+1.6-1.4. The combination of this result with other CMS searches for the Higgs boson decaying to a b-quark pair yields a signal strength of 1.0±0.4, corresponding to a signal significance of 2.6 standard deviations for a Higgs boson mass of 125 GeV.
Search For The Standard Model Higgs Boson Produced In Association With A Standard W Or A Z Boson And Decaying To Bottom Quarks
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Author :
language : en
Publisher:
Release Date : 2014
Search For The Standard Model Higgs Boson Produced In Association With A Standard W Or A Z Boson And Decaying To Bottom Quarks written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
A search for the standard model Higgs boson (H) decaying to b b-bar when produced in association with a weak vector boson (V) is reported for the following channels: W(mu nu)H, W(e nu)H, W(tau nu)H, Z(mu mu)H, Z(e e)H, and Z(nu nu)H. The search is performed in data samples corresponding to integrated luminosities of up to 5.1 inverse femtobarns at sqrt(s) = 7 TeV and up to 18.9 inverse femtobarns at sqrt(s) = 8 TeV, recorded by the CMS experiment at the LHC. An excess of events is observed above the expected background with a local significance of 2.1 standard deviations for a Higgs boson mass of 125 GeV, consistent with the expectation from the production of the standard model Higgs boson. The signal strength corresponding to this excess, relative to that of the standard model Higgs boson, is 1.0 +/- 0.5./abstract
Search Of The Higgs Boson Produced Through Vector Boson Fusion Decaying To A Pair Of Bb With The Atlas Detector
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Author : Zihao Jiang
language : en
Publisher:
Release Date : 2019
Search Of The Higgs Boson Produced Through Vector Boson Fusion Decaying To A Pair Of Bb With The Atlas Detector written by Zihao Jiang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
This thesis presents the search of the Higgs boson produced by Vector Boson Fusion (VBF) and decaying to bottom quarks. A search using the ATLAS detector was performed with 2016 proton-proton collision data. The multi-variate analysis measured the signal strengths of both the inclusive Higgs production and the vector-boson fusion production relative to the Standard Model prediction. This analysis led to the observation of Higgs coupling to b-quarks in the summer of 2018. Furthermore, potential improvements of the analysis techniques using complex neural networks are investigated. In order to understand better the Quantum Chromodynamics (QCD) backgrounds of the Higgs search, the characteristic variables of the gluon splitting vertex are measured.
A Search For Higgs Boson Production Via Vector Boson Fusion In Association With A Photon In The H Rarr B B Channel With The Atlas Detector
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Author : Peyton Wells Rose
language : en
Publisher:
Release Date : 2016
A Search For Higgs Boson Production Via Vector Boson Fusion In Association With A Photon In The H Rarr B B Channel With The Atlas Detector written by Peyton Wells Rose and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
A search for the Standard Model Higgs boson produced via vector boson fusion in association with a photon and decaying to a bottom quark-antiquark pair has been conducted using 12.6 fb--1 of proton-proton collision data collected by the ATLAS detector at a center-of-mass energy [sqrt] s =13TeV at the LHC in 2015 and 2016. The search benefits from a large reduction of the non-resonant multijet background relative to similar searches that do not explicitly require a photon and from efficient triggering aided by the presence of the photon. Multivariate techniques trained using simulated Monte Carlo samples are used to enhance the sensitivity of the analysis by constructing regions of phase space with higher expected signal fractions relative to the background. Data-driven techniques are used in those regions to provide a reliable estimate of the di-b-jet invariant mass spectrum of the non-resonant background. The final statistical analysis of the data relies on a profile likelihood fit to the di-b-jet invariant mass distribution, searching for a signal bump in an otherwise smoothly falling distribution. There is no observed excess above the background-only expectation, and the observed (expected) 95% confidence level upper limit on the production cross section times branching ratio for a Higgs boson mass of 125 GeV is 4.0 (6.0+2.3--1.7) times the Standard Model expectation. The observed signal strength is --3.9 +2.8--2.7 times the Standard Model value. This analysis is also sensitive to Z + gamma production: the observed (expected) upper limit is 2.0 (1.8+0.7-0.5) times the Standard Model expectation with an observed signal strength of 0.3+/-0.8.
Search For Invisible Decays Of Higgs Bosons In The Vector Boson Fusion And Associated Zh Production Modes
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Author :
language : en
Publisher:
Release Date : 2014
Search For Invisible Decays Of Higgs Bosons In The Vector Boson Fusion And Associated Zh Production Modes written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
A search for invisible decays of Higgs bosons is performed using the vector boson fusion and associated ZH production modes. In the ZH mode, the Z boson is required to decay to a pair of charged leptons or a b b-bar quark pair. The searches use the 8 TeV pp collision dataset collected by the CMS detector at the LHC, corresponding to an integrated luminosity of up to 19.7 inverse femtobarns. Certain channels include data from 7 TeV collisions corresponding to an integrated luminosity of 4.9 inverse femtobarns. The searches are sensitive to non-standard-model invisible decays of the recently observed Higgs boson, as well as additional Higgs bosons with similar production modes and large invisible branching fractions. In all channels, the observed data are consistent with the expected standard model backgrounds. Limits are set on the production cross section times invisible branching fraction, as a function of the Higgs boson mass, for the vector boson fusion and ZH production modes. By combining all channels, and assuming standard model Higgs boson cross sections and acceptances, the observed (expected) upper limit on the invisible branching fraction at m[H] = 125 GeV is found to be 0.58 (0.44) at 95% confidence level. We interpret this limit in terms of a Higgs-portal model of dark matter interactions.
A Search For The Standard Model Higgs Boson In The Process Zh Rightarrow Ell Ell B Bar B In 4 1 Unit 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 Rightarrow Ell Ell B Bar B In 4 1 Unit 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{sup ±}, 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{sup ±} and the Z bosons, as predicted by the standard model. The latest experimental averages for the masses of the top quark, W{sup ±} 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{sup {+-}} 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 --> ll−b{bar 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 --> ll−), while the Higgs decays to a bottom anti-bottom quark pair (H --> b{bar 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{bar 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{bar 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 selection applied to isolate ZH --> l+l−b{bar b} candidate events from the data sample, and the advanced techniques employed to maximize the separation of the signal from background processes. Chapters 9 and 10 present the systematic uncertainties affecting our modeling of the data sample and the results of the search. Chapter 11 presents a discussion of ZH --> l+l−b{bar b} in the context of the overall Tevatron efforts to observe a standard model Higgs signal.
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...
Search For The Standard Model Higgs Boson Produced Via Vector Boson Fusion And Decaying To Bottom Quarks With The Cms Detector At The Large Hadron Collider
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Author : Sara Alderweireldt
language : en
Publisher:
Release Date : 2016
Search For The Standard Model Higgs Boson Produced Via Vector Boson Fusion And Decaying To Bottom Quarks With The Cms Detector At The Large Hadron Collider written by Sara Alderweireldt and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
Search For The Standard Model Higgs Boson Produced In Association With A Vector Boson And Decaying To A B Quark Pair With The Atlas Detector
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Author : Ben Harry Smart
language : en
Publisher:
Release Date : 2015
Search For The Standard Model Higgs Boson Produced In Association With A Vector Boson And Decaying To A B Quark Pair With The Atlas Detector written by Ben Harry Smart and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Search For The Standard Model Higgs Boson Decaying Into B Overline B Produced In Association With Top Quarks Decaying Hadronically In Pp Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2016
Search For The Standard Model Higgs Boson Decaying Into B Overline B Produced In Association With Top Quarks Decaying Hadronically In Pp 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 2016 with categories.
In this paper, a search for Higgs boson production in association with a pair of top quarks ($ t\overline{t} $H) is performed, where the Higgs boson decays to $ b\overline{b} $ , and both top quarks decay hadronically. The data used correspond to an integrated luminosity of 20.3 fb -1 of pp collisions at √s = 8 TeV collected with the ATLAS detector at the Large Hadron Collider. The search selects events with at least six energetic jets and uses a boosted decision tree algorithm to discriminate between signal and Standard Model background. The dominant multijet background is estimated using a dedicated data-driven technique. For a Higgs boson mass of 125 GeV, an upper limit of 6.4 (5.4) times the Standard Model cross section is observed (expected) at 95% confidence level. The best-fit value for the signal strength is [mu] = 1.6 ± 2.6 times the Standard Model expectation for mH = 125 GeV. Combining all $ t\overline{t}$H searches carried out by ATLAS at √s = 8 and 7 TeV, an observed (expected) upper limit of 3.1 (1.4) times the Standard Model expectation is obtained at 95% confidence level, with a signal strength [mu] = 1.7 ± 0.8.