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| Author | : Ravi Shekhar |
| Publisher | : |
| Total Pages | : 198 |
| Release | : 2009 |
| Genre | : Higgs bosons |
| ISBN | : |
| Author | : |
| Publisher | : |
| Total Pages | : 110 |
| Release | : 2009 |
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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.
| Author | : |
| Publisher | : |
| Total Pages | : 153 |
| Release | : 2007 |
| Genre | : |
| ISBN | : |
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.
| Author | : Jonathan Zvi Efron |
| Publisher | : |
| Total Pages | : 132 |
| Release | : 2007 |
| Genre | : Higgs bosons |
| ISBN | : |
Abstract: 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, his 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.
| Author | : |
| Publisher | : |
| Total Pages | : 179 |
| Release | : 2008 |
| Genre | : |
| ISBN | : |
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.
| Author | : |
| Publisher | : |
| Total Pages | : 153 |
| Release | : 2007 |
| Genre | : |
| ISBN | : |
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.
| Author | : |
| Publisher | : |
| Total Pages | : 179 |
| Release | : 2008 |
| Genre | : |
| ISBN | : |
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.
| Author | : Brandon Scott Parks |
| Publisher | : |
| Total Pages | : 150 |
| Release | : 2008 |
| Genre | : Higgs bosons |
| ISBN | : |
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.
| Author | : |
| Publisher | : |
| Total Pages | : |
| Release | : 2011 |
| Genre | : |
| ISBN | : |
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.
| Author | : Justin Robert Pilot |
| Publisher | : |
| Total Pages | : 131 |
| Release | : 2011 |
| Genre | : |
| ISBN | : |
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.
