Search For The Higgs Boson In The Zh To Mu Mu B Bar B Channel At Cdf Using Novel Multivariate Techniques
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Search For The Higgs Boson In The Zh To Mu Mu B Bar B Channel At Cdf Using Novel Multivariate Techniques
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Author :
language : en
Publisher:
Release Date : 2011
Search For The Higgs Boson In The Zh To Mu Mu B Bar B Channel At Cdf Using Novel Multivariate Techniques 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 the Standard Model Higgs Boson using the process $ZH\to\mu^+\mu^- b\bar{b}$. We use a dataset corresponding to 9.2 fb$^{-1}$ of integrated luminosity from proton-antiproton collisions with center-of-mass energy 1.96 TeV at the Fermilab Tevatron, collected with the CDF II detector. This analysis benefits from several new multivariate techniques that have not been used in previous analyses at CDF. We use a multivariate function to select muon candidates, increasing signal acceptance while simultaneously keeping fake rates small. We employ an inclusive trigger selection to further increase acceptance. To enhance signal discrimination, we utilize a multi-layer approach consisting of expert discriminants. This multi-layer discriminant method helps isolate the two main classes of background events, $t\bar{t}$ and $Z$+jets production. It also includes a flavor separator, to distinguish light flavor jets from jets consistent with the decay of a $B$-hadron. Wit h this novel multi-layer approach, we proceed to set limits on the $ZH$ production cross section times branching ratio. For a Higgs boson with mass 115 GeV/$c^2$, we observe (expect) a limit of 8.0 (4.9) times the Standard Model prediction.
Search For The Higgs Boson In The Zh To Uubb Channel At Cdf Using Novel Multivariate Techniques
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Author : Justin Robert Pilot
language : en
Publisher:
Release Date : 2011
Search For The Higgs Boson In The Zh To Uubb Channel At Cdf Using Novel Multivariate Techniques written by Justin Robert Pilot 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.
Abstract: We present a search for the Standard Model Higgs Boson using the process ZH to uubb. We use a dataset corresponding to 9.2/fb of integrated luminosity from proton-antiproton collisions with center-of-mass energy 1.96 TeV at the Fermilab Tevatron, collected with the CDF II detector. This analysis benefits from several new multivariate techniques that have not been used in previous analyses at CDF. We use a multivariate function to select muon candidates, increasing signal acceptance while simultaneously keeping fake rates small. We employ an inclusive trigger selection to further increase acceptance. To enhance signal discrimination, we utilize a multi-layer approach consisting of expert discriminants. This multi-layer discriminant method helps isolate the two main classes of background events, t-tbar and Z+jets production. It also includes a flavor separator, to distinguish light flavor jets from jets consistent with the decay of a B-hadron. With this novel multi-layer approach, we proceed to set limits on the ZH production cross section times branching ratio. For a Higgs boson with mass 115 GeV/c^2, we observe (expect) a limit of 8.0 (4.9) times the Standard Model prediction.
Search For The Standard Model Higgs Boson In Zh 2 Mu Mu B Bar B Production At D And Evidence For The H2 B Bar B Decay At The Tevatron
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Author :
language : en
Publisher:
Release Date : 2014
Search For The Standard Model Higgs Boson In Zh 2 Mu Mu B Bar B Production At D And Evidence For The H2 B Bar B Decay 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 2014 with categories.
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$\bar{b}$.
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.
Search For The Higgs Boson In The Zh U2192 Vvb Bar B Channel At Cdf Run Ii
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Author :
language : en
Publisher:
Release Date : 2008
Search For The Higgs Boson In The Zh U2192 Vvb Bar B Channel 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 2008 with categories.
This analysis focuses on a low mass Higgs boson search with 1.7 fb-1 of data. The focus is on Higgs events in which it is produced in association with a W or Z boson. Such events are expected to leave a distinct signature of large missing transverse energy for either a Z → vv decay or a leptonic W decay in which the lepton goes undetected, as well as jets with taggable secondary vertices from the H → b$ar{b}$ decay. Utilizing a new track based technique for removing QCD multi-jet processes as well as a neural network discriminant, an expected limit of 8.3 times the Standard Model prediction at the 95% CL for a Higgs boson mass of 115 GeV/c2 is calculated, with an observed limit of 8.0*SM.
Search For The Higgs Boson In The Zh Vvbb Channel At Cdf Run Ii
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Author :
language : en
Publisher:
Release Date : 2008
Search For The Higgs Boson In The Zh Vvbb Channel 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 2008 with categories.
This analysis focuses on a low mass Higgs boson search with 1.7 fb−1 of data. The focus is on Higgs events in which it is produced in association with a W or Z boson. Such events are expected to leave a distinct signature of large missing transverse energy for either a Z → [nu][nu] decay or a leptonic W decay in which the lepton goes undetected, as well as jets with taggable secondary vertices from the H → b{bar B} decay. Utilizing a new track based technique for removing QCD multi-jet processes as well as a neural network discriminant, an expected limit of 8.3 times the Standard Model prediction at the 95% CL for a Higgs boson mass of 115 GeV/c2 is calculated, with an observed limit of 8.0*SM.
A Search For The Higgs Boson In The Zh Dilepton Decay Channel At Cdf Ii
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Author :
language : en
Publisher:
Release Date : 2009
A Search For The Higgs Boson In The Zh Dilepton Decay Channel 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.
This dissertation describes a search for the Standard Model Higgs boson produced in association with the Z boson via Higgs-strahlung at the CDF II detector at the Tevatron. At a Higgs boson mass between 100 GeV/c2 and 135 GeV/c2, the primary Higgs decay mode is to a pair of b quarks. The associated Z boson can decay to a pair of electrons or muons, allowing detection of a final event signature of two visible leptons and two b quarks. This final state allows reduction of large QCD backgrounds compared to a hadronic Z boson decay, leading to a more sensitive search. To increase sensitivity, standard model matrix element probabilities for ZH signal and the dominant backgrounds are used as components to a likelihood fit in signal fraction. In 2.7 fb−1 of CDF II data, we see no evidence of production of a Higgs boson with a mass between 100 GeV c2 and 150 GeV/c2. Using the Feldman-Cousins technique to set a limit, at 95% coverage and a Higgs boson mass of 115 GeV/c2, the median expected limit was 12.1 x [sigma]{sub SM} and a limit of 8.2 x [sigma]{sub SM} was observed, where [sigma]{sub SM} is the NNLO theoretical cross section of p{bar p} →ZH → l +l -b{bar b} at √s=1.96 TeV . Cross section limits are computed at a range of Higgs boson mass values between 100 GeV/c 2 and 150 GeV/c2.
Search For The Higgs Boson In The Zh To Vvbb Channel At Cdf Run Ii
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Author : Brandon Scott Parks
language : en
Publisher:
Release Date : 2008
Search For The Higgs Boson In The Zh To Vvbb Channel At Cdf Run Ii written by Brandon Scott Parks and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with Higgs bosons categories.
Abstract: This analysis focuses on a low mass Higgs boson search with 1.7 fb^-1 of data. The focus is on Higgs events in which it is produced in association with a W or Z boson. Such events are expected to leave a distinct signature of large missing transverse energy for either a Z to vv decay or a leptonic W decay in which the lepton goes undetected, as well as jets with taggable secondary vertices from the H to bb decay. Utilizing a new track based technique for removing QCD multi-jet processes as well as a neural network discriminant, an expected limit of 8.3 times the Standard Model prediction at the 95% CL for a Higgs boson mass of 115 GeV/c^2 is calculated, with an observed limit of 8.0*SM.
Search For The Higgs Boson In The H Ww Lvlv Channel Using Multivariate Analysis Techniques
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Author : Matthew Bluteau
language : en
Publisher:
Release Date : 2013
Search For The Higgs Boson In The H Ww Lvlv Channel Using Multivariate Analysis Techniques written by Matthew Bluteau and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Search For The Higgs Boson In The Zh To L L B Bar B Channel At Cdf Run Ii
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Author :
language : en
Publisher:
Release Date : 2007
Search For The Higgs Boson In The Zh To L L B Bar B Channel 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 2007 with categories.
The Standard Model of particle physics is in excellent agreement with the observed phenomena of particle physics. Within the Standard Model, the weak and electromagnetic forces are successfully combined. However, this combination is only valid if the masses of the force carriers of the weak force, the Z and W bosons, are massless. In fact, these two particles are the second and third most massive observed elementary particles. Within the minimal Standard Model, the Higgs mechanism is introduced to reconcile this contradiction. Conclusive proof of this theory would come with the discovery of the Higgs boson.