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A Search For The Standard Model Neutral Higgs Boson In The He E And Hmu Mu Channels In Z Degree Decays
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Book Synopsis A Search for the Standard Model Neutral Higgs Boson in the He+e- and H[mu]+[mu]- Channels in Z [degree] Decays by : John M. Hilgart
Download or read book A Search for the Standard Model Neutral Higgs Boson in the He+e- and H[mu]+[mu]- Channels in Z [degree] Decays written by John M. Hilgart and published by . This book was released on 1990 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Search for the Standard Model Neutral Higgs Boson in the He+e- and Hu+u- Channels in Z Decays by : John M. Hilgart
Download or read book A Search for the Standard Model Neutral Higgs Boson in the He+e- and Hu+u- Channels in Z Decays written by John M. Hilgart and published by . This book was released on 1990* with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Search for the Standard Model Higgs Boson in the H → ZZ → l + l - qq Decay Channel at CMS by : Francesco Pandolfi
Download or read book Search for the Standard Model Higgs Boson in the H → ZZ → l + l - qq Decay Channel at CMS written by Francesco Pandolfi and published by Springer Science & Business Media. This book was released on 2013-08-15 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: The theoretical foundations of the Standard Model of elementary particles relies on the existence of the Higgs boson, a particle which has been revealed for the first time by the experiments run at the Large Hadron Collider (LHC) in 2012. As the Higgs boson is an unstable particle, its search strategies were based on its decay products. In this thesis, Francesco Pandolfi conducted a search for the Higgs boson in the H → ZZ → l + l - qq Decay Channel with 4.6 fb -1 of 7 TeV proton-proton collision data collected by the Compact Muon Solenoid (CMS) experiment. The presence of jets in the final state poses a series of challenges to the experimenter: both from a technical point of view, as jets are complex objects and necessitate of ad-hoc reconstruction techniques, and from an analytical one, as backgrounds with jets are copious at hadron colliders, therefore analyses must obtain high degrees of background rejection in order to achieve competitive sensitivity. This is accomplished by following two directives: the use of an angular likelihood discriminant, capable of discriminating events likely to originate from the decay of a scalar boson from non-resonant backgrounds, and by using jet parton flavor tagging, selecting jets compatible with quark hadronization and discarding jets more likely to be initiated by gluons. The events passing the selection requirements in 4.6 fb -1 of data collected by the CMS detector are examined, in the search of a possible signal compatible with the decay of a heavy Higgs boson. The thesis describes the statistical tools and the results of this analysis. This work is a paradigm for studies of the Higgs boson with final states with jets. The non-expert physicists will enjoy a complete and eminently readable description of a proton-proton collider analysis. At the same time, the expert reader will learn the details of the searches done with jets at CMS.
Book Synopsis Search for the Standard Model Higgs Boson Produced in Association with a Standard W Or a Z Boson and Decaying to Bottom Quarks by :
Download or read book 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 published by . This book was released on 2014 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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
Book Synopsis Search for Neutral MSSM Higgs Bosons Decaying to $\mu^{+} \mu^{-}$ in Pp Collisions at $ \sqrt{s} by :
Download or read book Search for Neutral MSSM Higgs Bosons Decaying to $\mu^{+} \mu^{-}$ in Pp Collisions at $ \sqrt{s} written by and published by . This book was released on 2015 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for neutral Higgs bosons predicted in the minimal supersymmetric standard model (MSSM) for [mu]+[mu]- decay channels is presented. Our analysis uses data collected by the CMS experiment at the LHC in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV, corresponding to integrated luminosities of 5.1 and 19.3 fb-1, respectively. The search is sensitive to Higgs bosons produced either through the gluon fusion process or in association with a bb quark pair. No statistically significant excess is observed in the [mu]+[mu]- mass spectrum. Results are interpreted in the framework of several benchmark scenarios, and the data are used to set an upper limit on the MSSM parameter tan [beta] as a function of the mass of the pseudoscalar A boson in the range from 115 to 300 GeV. Furthermore, the model independent upper limits are given for the product of the cross section and branching fraction for gluon fusion and b quark associated production at √s = 8 TeV. As a result, they are the most stringent limits obtained to date in this channel.
Book Synopsis Searches for the Standard Model Higgs Boson in the Leptonic Decay Channels by : Jin Yamamoto
Download or read book Searches for the Standard Model Higgs Boson in the Leptonic Decay Channels written by Jin Yamamoto and published by . This book was released on 2002 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Searches for Pair-produced Charged Higgs Bosons and Neutral Supersymmetric Higgs Bosons in Z [degree] Decays by : Douglas F. Cowen
Download or read book Searches for Pair-produced Charged Higgs Bosons and Neutral Supersymmetric Higgs Bosons in Z [degree] Decays written by Douglas F. Cowen and published by . This book was released on 1990 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Search for the Standard Model Higgs Boson in the Z Gamma Channel by : Kevin Singh
Download or read book Search for the Standard Model Higgs Boson in the Z Gamma Channel written by Kevin Singh and published by . This book was released on 2013 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Higgs decay into a photon and a Z boson, with the Z boson decaying into an electron-positron pair (electron channel) or muon-antimuon pair (muon channel), allows for accurate reconstructions of the Higgs boson mass and measurement of the Higgs to Z-[gamma] coupling. We explore selection criteria for the photon and the two leptons and provide preliminary observed and expected limits for the Higgs boson production cross section in the mass range from 120 GeV to 150 GeV. The data used in this analysis was collected with the CMS detector and corresponds to 5 fb- 1 and 19 fb-1 at center-of-mass energies of 7 TeV and 8 TeV, respectively.
Book Synopsis Search for a Standard Model-like Higgs Boson in the [mu]^+[mu]^- and E^+e^- Decay Channels at the LHC. by :
Download or read book Search for a Standard Model-like Higgs Boson in the [mu]^+[mu]^- and E^+e^- Decay Channels at the LHC. written by and published by . This book was released on 2015 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search is presented for a standard model-like Higgs boson decaying to the [mu]+[mu]- ore+e- final states based on proton-proton collisions recorded by the CMS experiment at the CERN LHC. The data correspond to integrated luminosities of 5.0 fb-1 at a centre-of-mass energy of 7 TeV and 19.7 fb-1 at 8 TeV for the [mu]+[mu]- search, and of 19.7 fb-1 at 8 TeV for the e+e- search. Upper limits on the production cross section times branching fraction at the 95% confidence level are reported for Higgs boson masses in the range from 120 to 150 GeV. For a Higgs boson with a mass of 125 GeV decaying to [mu]+[mu]-, the observed (expected) upper limit on the production rate is found to be 7.4 () times the standard model value. This corresponds to an upper limit on the branching fraction of 0.0016. Similarly, for e+e-, an upper limit of 0.0019 is placed on the branching fraction, which is H".7×105 times the standard model value. These results, together with recent evidence of the 125 GeV boson coupling to [tau]-leptons with a larger branching fraction consistent with the standard model, confirm that the leptonic couplings of the new boson are not flavour-universal.
Book Synopsis Search for Neutral Higgs Bosons in E+e- Interactions at Center-of-mass Energies Between 130 GeV and 183 GeV by : David Aaron Matzner Dominguez
Download or read book Search for Neutral Higgs Bosons in E+e- Interactions at Center-of-mass Energies Between 130 GeV and 183 GeV written by David Aaron Matzner Dominguez and published by . This book was released on 1998 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Search for the Standard Model Higgs Boson in the Z Boson-H Boson Decaying to Positive Muon-negative Muon and Bottom-anti-bottom Quark Channel in Proton-antiproton Collisions at the Center of Mass Energy by :
Download or read book Search for the Standard Model Higgs Boson in the Z Boson-H Boson Decaying to Positive Muon-negative Muon and Bottom-anti-bottom Quark Channel in Proton-antiproton Collisions at the Center of Mass Energy written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Search for the standard model Higgs boson in the Z boson-H boson decaying to positive muon-negative muon and bottom-anti-bottom quark channel in proton-antiproton collisions at the center of mass energy = 1.96 TeV.
Book Synopsis First Search for the Standard Model Higgs Boson Using the Semileptonic Decay Channel by :
Download or read book First Search for the Standard Model Higgs Boson Using the Semileptonic Decay Channel written by and published by . This book was released on 2010 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents the first search for the standard model Higgs boson (H) in decay topologies containing a muon, an imbalance in transverse momentum (E{sub T}) and jets, using p{bar 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 → [mu][nu]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 M{sub H} in the range of 115-200 GeV. For M{sub H} = 165 GeV, the observed and expected limits are factors of 11.2 larger than the standard model value. Combining this channel with e[nu]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.
Book Synopsis 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 by :
Download or read book 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 written by and published by . This book was released on 2014 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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$\bar{b}$.
Book Synopsis Search for the Standard Model Higgs Boson in the Decay Mode H-] WW-] Lnulnu by :
Download or read book Search for the Standard Model Higgs Boson in the Decay Mode H-] WW-] Lnulnu written by and published by . This book was released on 2009 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Search for the Standard Model Higgs Boson Produced in Association with a Z Boson in the Electron-muon Final State and the Higgs Boson Decaying Into Bottom Quarks by : Rachel A. Bartek
Download or read book Search for the Standard Model Higgs Boson Produced in Association with a Z Boson in the Electron-muon Final State and the Higgs Boson Decaying Into Bottom Quarks written by Rachel A. Bartek and published by . This book was released on 2013 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for the standard model Higgs boson is presented in the associated production channel Z ([Pi]) H (bb ) where each tau decays leptonically, one to an electron, the other to a muon and associated neutrinos. A data sample comprising of 5.0 fb[superscript -1] and 19.0 fb[superscript -1] from the 2011 and 2012 proton collision running periods at a center of mass of 7 and 8TeV, respectively, has been analyzed and 95% C.L. upper limits derived for Higgs masses of 110-135 GeV. vi
Book Synopsis 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} by :
Download or read book 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 published by . This book was released on 2010 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Search for a Higgs Boson in the Decay Channel $H$ to ZZ(*) to $q$ Qbar $\ell-̂$ L+ in $pp$ Collisions at $\sqrt{s} by :
Download or read book Search for a Higgs Boson in the Decay Channel $H$ to ZZ(*) to $q$ Qbar $\ell-̂$ L+ in $pp$ Collisions at $\sqrt{s} written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for the standard model Higgs boson decaying into two Z bosons with subsequent decay into a final state containing two quark jets and two leptons, H to ZZ(*) to q q-bar l-l+ is presented. Results are based on data corresponding to an integrated luminosity of 4.6 inverse femtobarns of proton-proton collisions at sqrt(s)=7 TeV, collected with the CMS detector at the LHC. In order to discriminate between signal and background events, kinematic and topological quantities, including the angular spin correlations of the decay products, are employed. Events are further classified according to the probability of the jets to originate from quarks of light or heavy flavor or from gluons. No evidence for the Higgs boson is found, and upper limits on its production cross section are determined for a Higgs boson of mass between 130 and 600 GeV.
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