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Title: Search for WH Associated Production in the l upsilon b-bbar Final State Using the DØ Detector at the Tevatron

Abstract

The Standard Model is the framework which allows to describe interactions between particles and their dynamics. The Higgs mechanism is a solution to naturally introduce a mass term in the theoretical description of this model. After electroweak spontaneous symmetry breaking, a new massive scalar particle is introduced, the Higgs boson. Since it hasn’t been discovered yet, the search for the Higgs boson is carried at the Tevatron, which is a p$$\bar{p}$$ collider at a center-of-mass of 1.96 TeV. For M H <115 GeV, the dominant decay mode is H → b$$\bar{b}$$ . The analysis presented in this document is focused on the 100< M H <150 GeV mass range, in the channel where the Higgs boson is produced in assocation with a W boson which decays either to an electron or muon and a neutrino. The study of this final state relies on informations collected from all parts of the DØ detector. A result based on 5.3 fb -1 of RunII Tevatron collisions is presented here. In order to increase the sensitivity to the signal, the analysis is separated in different sub-channels according to the lepton flavour, number of jets in the final state, number of jets identified as originated from b quarks and data taking periods. After selecting events, a multivariate analysis technique is used to separate signal-like events from the expected physics and instrumental backgrounds. A good agreement between data and simulation is observed. As no signal excess is observed in data, an observed (expected) upper limit of 4.5 (4.8) for M H = 115 GeV is set on the ratio of the WH cross section multiplied by the H → b$$\bar{b}$$ branching fraction to its standard model prediction, at 95% confidence level. Since the final Tevatron dataset is soon to be analyzed, an effort is brought to achieve the maximum sensitivity. A preliminary analysis updated in Summer 2011 is presented as well as future improvements to be considered in the final publication for the search in the WH → ℓνb$$\bar{b}$$ channel. Since the dijet invariant mass is the most discriminant single variable, a correction based on jet shapes is derived to improve the mass resolution, hence the analysis sensitivity. Moreover, a different usage of b-jets identification tools and optimization studies on the final discriminant yields a significant improvement. This result is part of the Tevatron Higgs combination.

Authors:
 [1]
  1. Paris Diderot Univ. (France)
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1128098
Report Number(s):
FERMILAB-THESIS-2011-61
DOE Contract Number:  
AC02-07CH11359
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; tevatron; D0; higgs boson; WH; multivariate analysis techinques; jet energy resolution

Citation Formats

Brown, Jonathan. Search for WH Associated Production in the l upsilon b-bbar Final State Using the DØ Detector at the Tevatron. United States: N. p., 2011. Web. doi:10.2172/1128098.
Brown, Jonathan. Search for WH Associated Production in the l upsilon b-bbar Final State Using the DØ Detector at the Tevatron. United States. doi:10.2172/1128098.
Brown, Jonathan. Thu . "Search for WH Associated Production in the l upsilon b-bbar Final State Using the DØ Detector at the Tevatron". United States. doi:10.2172/1128098. https://www.osti.gov/servlets/purl/1128098.
@article{osti_1128098,
title = {Search for WH Associated Production in the l upsilon b-bbar Final State Using the DØ Detector at the Tevatron},
author = {Brown, Jonathan},
abstractNote = {The Standard Model is the framework which allows to describe interactions between particles and their dynamics. The Higgs mechanism is a solution to naturally introduce a mass term in the theoretical description of this model. After electroweak spontaneous symmetry breaking, a new massive scalar particle is introduced, the Higgs boson. Since it hasn’t been discovered yet, the search for the Higgs boson is carried at the Tevatron, which is a p$\bar{p}$ collider at a center-of-mass of 1.96 TeV. For MH <115 GeV, the dominant decay mode is H → b$\bar{b}$ . The analysis presented in this document is focused on the 100< MH <150 GeV mass range, in the channel where the Higgs boson is produced in assocation with a W boson which decays either to an electron or muon and a neutrino. The study of this final state relies on informations collected from all parts of the DØ detector. A result based on 5.3 fb-1 of RunII Tevatron collisions is presented here. In order to increase the sensitivity to the signal, the analysis is separated in different sub-channels according to the lepton flavour, number of jets in the final state, number of jets identified as originated from b quarks and data taking periods. After selecting events, a multivariate analysis technique is used to separate signal-like events from the expected physics and instrumental backgrounds. A good agreement between data and simulation is observed. As no signal excess is observed in data, an observed (expected) upper limit of 4.5 (4.8) for MH = 115 GeV is set on the ratio of the WH cross section multiplied by the H → b$\bar{b}$ branching fraction to its standard model prediction, at 95% confidence level. Since the final Tevatron dataset is soon to be analyzed, an effort is brought to achieve the maximum sensitivity. A preliminary analysis updated in Summer 2011 is presented as well as future improvements to be considered in the final publication for the search in the WH → ℓνb$\bar{b}$ channel. Since the dijet invariant mass is the most discriminant single variable, a correction based on jet shapes is derived to improve the mass resolution, hence the analysis sensitivity. Moreover, a different usage of b-jets identification tools and optimization studies on the final discriminant yields a significant improvement. This result is part of the Tevatron Higgs combination.},
doi = {10.2172/1128098},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2011},
month = {9}
}

Thesis/Dissertation:
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