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Search for the Higgs boson in the $WH \to ℓνb\overline{b}$ channel with the ATLAS detector - Development of high performance $b$-jet identification algorithms
In July 2012, the ATLAS and CMS collaborations announced the discovery of a new particle at a mass of about 125 GeV, compatible with the Higgs boson predicted by the Standard Model (SM) of particle physics. Although all measurements as of Summer 2015 show a full consistency with the SM predictions,...
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Lenguaje: | eng |
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2016
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Acceso en línea: | http://cds.cern.ch/record/2227038 |
_version_ | 1780952431246442496 |
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author | Mochizuki, Kazuya |
author_facet | Mochizuki, Kazuya |
author_sort | Mochizuki, Kazuya |
collection | CERN |
description | In July 2012, the ATLAS and CMS collaborations announced the discovery of a new particle at a mass of about 125 GeV, compatible with the Higgs boson predicted by the Standard Model (SM) of particle physics. Although all measurements as of Summer 2015 show a full consistency with the SM predictions, the fermionic decay channels (H → bb and ττ) have not been seen yet as clearly as the bosonic decay channels. This thesis presents a search for the Higgs boson in the WH → ℓνbb channel, using proton-proton collision data at √s = 8 TeV taken with the ATLAS detector in the year 2012, corresponding to an integrated luminosity of 20.3 fb−1. This document details in particular one of the contributions made by the author in this search: the additional analysis region with muon events triggered by missing transverse momentum. An excess over the background-only hypothesis has been found with a significance of 1.8 σ while 1.5 σ was expected. The observed (expected) upper limit on the cross-section times branching ratio for WH → ℓνbb at 95% confidence level is found to be 2.35 (1.37) times the SM prediction at mH = 125 GeV. This search highly relies on the identification of jets originating in b-quark fragmentation, so-called b-tagging. In order to improve the H → bb search and other physics analyses using b-tagging in ATLAS, the development of high performance b-tagging algorithms has been performed and is presented also in this thesis. A new b-tagging algorithm, called MV2, is introduced: it improves the b-tagging performance significantly and is now the baseline b-tagging algorithm in ATLAS for the Run-2 analyses. |
id | cern-2227038 |
institution | Organización Europea para la Investigación Nuclear |
language | eng |
publishDate | 2016 |
record_format | invenio |
spelling | cern-22270382019-09-30T06:29:59Zhttp://cds.cern.ch/record/2227038engMochizuki, KazuyaSearch for the Higgs boson in the $WH \to ℓνb\overline{b}$ channel with the ATLAS detector - Development of high performance $b$-jet identification algorithmsParticle Physics - ExperimentIn July 2012, the ATLAS and CMS collaborations announced the discovery of a new particle at a mass of about 125 GeV, compatible with the Higgs boson predicted by the Standard Model (SM) of particle physics. Although all measurements as of Summer 2015 show a full consistency with the SM predictions, the fermionic decay channels (H → bb and ττ) have not been seen yet as clearly as the bosonic decay channels. This thesis presents a search for the Higgs boson in the WH → ℓνbb channel, using proton-proton collision data at √s = 8 TeV taken with the ATLAS detector in the year 2012, corresponding to an integrated luminosity of 20.3 fb−1. This document details in particular one of the contributions made by the author in this search: the additional analysis region with muon events triggered by missing transverse momentum. An excess over the background-only hypothesis has been found with a significance of 1.8 σ while 1.5 σ was expected. The observed (expected) upper limit on the cross-section times branching ratio for WH → ℓνbb at 95% confidence level is found to be 2.35 (1.37) times the SM prediction at mH = 125 GeV. This search highly relies on the identification of jets originating in b-quark fragmentation, so-called b-tagging. In order to improve the H → bb search and other physics analyses using b-tagging in ATLAS, the development of high performance b-tagging algorithms has been performed and is presented also in this thesis. A new b-tagging algorithm, called MV2, is introduced: it improves the b-tagging performance significantly and is now the baseline b-tagging algorithm in ATLAS for the Run-2 analyses.CERN-THESIS-2015-367oai:cds.cern.ch:22270382016-10-24T12:10:12Z |
spellingShingle | Particle Physics - Experiment Mochizuki, Kazuya Search for the Higgs boson in the $WH \to ℓνb\overline{b}$ channel with the ATLAS detector - Development of high performance $b$-jet identification algorithms |
title | Search for the Higgs boson in the $WH \to ℓνb\overline{b}$ channel with the ATLAS detector - Development of high performance $b$-jet identification algorithms |
title_full | Search for the Higgs boson in the $WH \to ℓνb\overline{b}$ channel with the ATLAS detector - Development of high performance $b$-jet identification algorithms |
title_fullStr | Search for the Higgs boson in the $WH \to ℓνb\overline{b}$ channel with the ATLAS detector - Development of high performance $b$-jet identification algorithms |
title_full_unstemmed | Search for the Higgs boson in the $WH \to ℓνb\overline{b}$ channel with the ATLAS detector - Development of high performance $b$-jet identification algorithms |
title_short | Search for the Higgs boson in the $WH \to ℓνb\overline{b}$ channel with the ATLAS detector - Development of high performance $b$-jet identification algorithms |
title_sort | search for the higgs boson in the $wh \to ℓνb\overline{b}$ channel with the atlas detector - development of high performance $b$-jet identification algorithms |
topic | Particle Physics - Experiment |
url | http://cds.cern.ch/record/2227038 |
work_keys_str_mv | AT mochizukikazuya searchforthehiggsbosoninthewhtolnboverlinebchannelwiththeatlasdetectordevelopmentofhighperformancebjetidentificationalgorithms |