Measurement of Higgs Boson Production Via Gluon Fusion and Vector-boson Fusion in the H->WW* Decay Mode with the ATLAS Experiment at the LHC at [square Root]s

Measurement of Higgs Boson Production Via Gluon Fusion and Vector-boson Fusion in the H->WW* Decay Mode with the ATLAS Experiment at the LHC at [square Root]s
Author: Ralf Gugel
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Total Pages:
Release: 2019
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Abstract: On the 4 th of July 2012 the observation of a new neutral particle was announced by the ATLAS [1] and CMS [2] Collaborations. This particle is by now generally considered as the Higgs boson H predicted [3, 4] in the Standard Model of particle physics. Its mass of m H = 125.09 ± 0.24 GeV [5] implies a rich set of final states which allow for experimental studies in regards to this particle and searches for deviations from the properties predicted by the Standard Model. In this thesis a measurement of the gluon-fusion and vector-boson fusion production cross sections times H→WW* branching ratio is presented using final states with one electron and one muon. The measurement is based on proton- proton collisions with an integrated luminosity of 36.1 fb -1 √ recorded with the ATLAS detector at the CERN Large Hadron Collider ( LHC ) at s = 13 TeV in 2015 and 2016. Signal-like events are selected in categories with different jet multiplicities. The results are extracted by means of a binned maximum-likelihood fit. To this end, either distributions in multiple discriminant variables or the response of a multivariate classifier are used depending on the category. The results are found to be well compatible with the Standard Model predictions. This analysis is extrapolated to estimate the future precision of such a measurement at the end of the High-Luminosity LHC programme [6]. This extrapolated analysis is combined with analogously extrapolated analyses targeting other production and decay modes of the Higgs boson. Based on this combination the expected precision is determined for future measurements of couplings between the Higgs boson and other particles. Thereby an estimation is given for the anticipated sensitivity of these analyses to signs of physics beyond the Standard Model. In addition studies are presented to identify sources of electron charge misidentification in the reconstruction algorithms employed in the ATLAS Collaboration.

Observation and Measurement of Higgs Boson Decays to WW* with the ATLAS Detector

Observation and Measurement of Higgs Boson Decays to WW* with the ATLAS Detector
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Release: 2015
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We report the observation of Higgs boson decays to WW* based on an excess over background of 6.1 standard deviations in the dilepton final state, where the Standard Model expectation is 5.8 standard deviations. Evidence for the vector-boson fusion (VBF) production process is obtained with a significance of 3.2 standard deviations. The results are obtained from a data sample corresponding to an integrated luminosity of 25 fb-1 from [arrow]"=7 and 8 TeV pp collisions recorded by the ATLAS detector at the LHC. For a Higgs boson mass of 125.36 GeV, the ratio of the measured value to the expected value of the total production cross section times branching fraction is 1.09+0.16-0.15(stat)+0.17-0.14(syst). The corresponding ratios for the gluon fusion and vector-boson fusion production mechanisms are 1.02 " 0.19(stat)+0.22-0.18(syst) and 1.27+0.44-0.40(stat)+0.30-0.21(syst), respectively. At [arrow]"=8 TeV, the total production cross sections are measured to be [sigma](gg 2!>H 2!WW*)=4.6"0.9(stat)+0.8-0.7(syst) pb and [sigma](VBF H 2!W*)=0.51+0.17-0.15(stat)+0.13-0.08(syst) pb. The fiducial cross section is determined for the gluon-fusion process in exclusive final states with 0 or one associated jet.

Measurement of Higgs Boson Production Via Gluon Fusion in the H →WW Decay Channel with the CMS Experiment

Measurement of Higgs Boson Production Via Gluon Fusion in the H →WW Decay Channel with the CMS Experiment
Author: Adrián Álvarez Fernández
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Release: 2021
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ISBN:

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This thesis reports measurements of the Higgs boson production in proton-proton collisions at a centre-of-mass energy of 13 TeV with data collected by the CMS experiment during the Run 2 operation period (2016-2018) of the Large Hadron Collider at CERN. The measurement is performed using a sample of event candidates to originate from the decay of a Higgs boson into a pair of W bosons, which then decay into a charged lepton and a neutrino resulting in a nal state with two charged leptons of dierent avour. The thesis focuses on the study of the Higgs boson production through the gluon fusion process, which is the most favoured one at a centre-of-mass energy of 13 TeV...

Precision Measurements of Higgs Boson Production in Decays to W Bosons Using Machine Learning with the ATLAS Experiment

Precision Measurements of Higgs Boson Production in Decays to W Bosons Using Machine Learning with the ATLAS Experiment
Author: Benjamin Jäger
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Total Pages: 0
Release: 2022
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The Higgs boson is a unique tool in the search for the fundamental laws of nature, as it is connected to many of the open fundamental questions the Standard Model (SM) of particle physics cannot answer. Precision measurements of the properties of the Higgs boson, including its interactions with other fundamental particles, provide a powerful tool to test the predictions of the SM and possibly find deviations from them. As part of a broad Higgs boson physics program at the Large Hadron Collider (LHC), this thesis presents cross-section measurements of Higgs boson production via gluon fusion (ggF) and vector-boson fusion (VBF) in decays to W bosons. The H -> WW* decay is the second most likely decay of the Higgs boson and, in the VBF production mode, the most sensitive channel to measure the coupling of the Higgs boson to vector bosons at the LHC. The measurement is based on pp collisions at a center-of-mass energy of \sqrt{s} = 13 TeV recorded by the ATLAS experiment at the LHC between 2015 and 2018, corresponding to an integrated luminosity of 139 / fb. The measurements of the inclusive ggF and VBF cross sections times branching fraction result in 12.0 +-1.4 pb and 0.75 +0.19 -0.16 pb, respectively. In addition, Higgs boson production is measured in 11 exclusive kinematic regions. All results are found to be consistent with their corresponding SM predictions. The H -> WW* analysis is also an important input to combined Higgs boson measurements, which provide some of the most precise measurements of Higgs boson interactions to date and are briefly summarized in this work. The measurement of the VBF, H -> WW* process is drastically improved over previous results by the implementation of a binary classifier based on a deep neural network (DNN) that distinguishes the VBF, H -> WW* signal from other physical processes. The development and optimization of the DNN are presented in this thesis. This thesis also presents the measurement of the jet energy resolution, which is essential for many physics analyses performed with the ATLAS experiment, such as the H -> WW* analysis, due to the abundance of jets in pp collisions.

Search for Higgs Boson Off-shell Production in Proton-proton Collisions at 7 and 8 TeV and Derivation of Constraints on Its Total Decay Width

Search for Higgs Boson Off-shell Production in Proton-proton Collisions at 7 and 8 TeV and Derivation of Constraints on Its Total Decay Width
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Total Pages: 44
Release: 2016
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ISBN:

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A search is presented for the Higgs boson off-shell production in gluon fusion and vector boson fusion processes with the Higgs boson decaying into a WW pair and the W bosons decaying leptonically. The data observed in this analysis are used to constrain the Higgs boson total decay width. The analysis is based on the data collected by the CMS experiment at the LHC, corresponding to integrated luminosities of 4.9 inverse femtobarns at a centre-of-mass energy of 7 TeV and 19.4 inverse femtobarns at 8 TeV, respectively. An observed (expected) upper limit on the off-shell Higgs boson event yield normalised to the standard model prediction of 2.4 (6.2) is obtained at the 95% CL for the gluon fusion process and of 19.3 (34.4) for the vector boson fusion process. Observed and expected limits on the total width of 26 and 66 MeV are found, respectively, at the 95% confidence level (CL). These limits are combined with the previous result in the ZZ channel leading to observed and expected 95% CL upper limits on the width of 13 and 26 MeV, respectively.