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Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS
This thesis presents a search for dark matter production in association with a Higgs boson decaying to a pair of bottom quarks, using data from 20.3\,fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of $8$ TeV collected by the ATLAS detector at the LHC. The dark matter particles are...
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Lenguaje: | eng |
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Springer
2017
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Acceso en línea: | https://dx.doi.org/10.1007/978-3-319-44218-1 http://cds.cern.ch/record/2102935 |
_version_ | 1780948752241000448 |
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author | Cheng, Yangyang |
author_facet | Cheng, Yangyang |
author_sort | Cheng, Yangyang |
collection | CERN |
description | This thesis presents a search for dark matter production in association with a Higgs boson decaying to a pair of bottom quarks, using data from 20.3\,fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of $8$ TeV collected by the ATLAS detector at the LHC. The dark matter particles are assumed to be Weakly Interacting Massive Particles, and can be produced in pairs at collider experiments. Events with large $E_T^{miss}$ are selected when produced in association with high momentum jets, of which at least two are identified as jets containing $b$-quarks consistent with those from a Higgs boson decay. To maintain good detector acceptance and selection efficiency of the signal across a wide kinematic range, two methods of Higgs boson reconstruction are used. The Higgs boson is reconstructed either as a pair of small-radius jets both containing $b$-quarks, called the ``resolved'' analysis, or as a single large-radius jet with substructure consistent with a high momentum $b\bar{b}$ system, called the ``boosted'' analysis. The resolved analysis is the focus of this thesis. The observed data are found to be consistent with the expected Standard Model backgrounds. The result from the resolved analysis is interpreted using a simplified model with a $Z^\prime$ gauge boson decaying into different Higgs bosons predicted in a two-Higgs-doublet model, of which the heavy pseudoscalar Higgs decays into a pair of dark matter particles. Exclusion limits are set in regions of parameter space for this model. Model-independent upper limits are also placed on the visible cross-sections for events with a Higgs boson decaying into $b\bar{b}$~and large missing transverse momentum with thresholds ranging from $150$ GeV to $400$ GeV. |
id | cern-2102935 |
institution | Organización Europea para la Investigación Nuclear |
language | eng |
publishDate | 2017 |
publisher | Springer |
record_format | invenio |
spelling | cern-21029352021-12-16T10:18:52Zdoi:10.1007/978-3-319-44218-1http://cds.cern.ch/record/2102935engCheng, YangyangSearch for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLASParticle Physics - ExperimentThis thesis presents a search for dark matter production in association with a Higgs boson decaying to a pair of bottom quarks, using data from 20.3\,fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of $8$ TeV collected by the ATLAS detector at the LHC. The dark matter particles are assumed to be Weakly Interacting Massive Particles, and can be produced in pairs at collider experiments. Events with large $E_T^{miss}$ are selected when produced in association with high momentum jets, of which at least two are identified as jets containing $b$-quarks consistent with those from a Higgs boson decay. To maintain good detector acceptance and selection efficiency of the signal across a wide kinematic range, two methods of Higgs boson reconstruction are used. The Higgs boson is reconstructed either as a pair of small-radius jets both containing $b$-quarks, called the ``resolved'' analysis, or as a single large-radius jet with substructure consistent with a high momentum $b\bar{b}$ system, called the ``boosted'' analysis. The resolved analysis is the focus of this thesis. The observed data are found to be consistent with the expected Standard Model backgrounds. The result from the resolved analysis is interpreted using a simplified model with a $Z^\prime$ gauge boson decaying into different Higgs bosons predicted in a two-Higgs-doublet model, of which the heavy pseudoscalar Higgs decays into a pair of dark matter particles. Exclusion limits are set in regions of parameter space for this model. Model-independent upper limits are also placed on the visible cross-sections for events with a Higgs boson decaying into $b\bar{b}$~and large missing transverse momentum with thresholds ranging from $150$ GeV to $400$ GeV.This thesis reports on the search for dark matter in data taken with the ATLAS detector at CERN’s Large Hadron Collider (LHC). The identification of dark matter and the determination of its properties are among the highest priorities in elementary particle physics and cosmology. The most likely candidate, a weakly interacting massive particle, could be produced in the high energy proton-proton collisions at the LHC. The analysis presented here is unique in looking for dark matter produced together with a Higgs boson that decays into its dominant decay mode, a pair of b quarks. If dark matter were seen in this mode, we would learn directly about the production mechanism because of the presence of the Higgs boson. This thesis develops the search technique and presents the most stringent production limit to date.SpringerCERN-THESIS-2015-211oai:cds.cern.ch:21029352017 |
spellingShingle | Particle Physics - Experiment Cheng, Yangyang Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS |
title | Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS |
title_full | Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS |
title_fullStr | Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS |
title_full_unstemmed | Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS |
title_short | Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS |
title_sort | search for dark matter produced in association with a higgs boson decaying to two bottom quarks at atlas |
topic | Particle Physics - Experiment |
url | https://dx.doi.org/10.1007/978-3-319-44218-1 http://cds.cern.ch/record/2102935 |
work_keys_str_mv | AT chengyangyang searchfordarkmatterproducedinassociationwithahiggsbosondecayingtotwobottomquarksatatlas |