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| Author | : Michael David Planer |
| Publisher | : |
| Total Pages | : 149 |
| Release | : 2018 |
| Genre | : |
| ISBN | : |
| Author | : Ahmed Tarek Abouelfadl Mohamed |
| Publisher | : Springer Nature |
| Total Pages | : 305 |
| Release | : 2020-11-12 |
| Genre | : Science |
| ISBN | : 3030595161 |
This thesis presents the measurement of the Higgs boson cross section in the diphoton decay channel. The measurement relies on proton-proton collision data at a center-of-mass energy √s = 13 TeV recorded by the ATLAS experiment at the Large Hadron Collider (LHC). The collected data correspond to the full Run-2 dataset with an integrated luminosity of 139 fb-1. The measured cross sections are used to constrain anomalous Higgs boson interactions in the Effective Field Theory (EFT) framework. The results presented in this thesis represent a reduction by a factor 2 of the different photon and jet energy scale and resolution systematic uncertainties with respect to the previous ATLAS publication. The thesis details the calibration of electron and photon energies in ATLAS, in particular the measurement of the presampler energy scale and the estimation of its systematic uncertainty. This calibration was used to perform a measurement of the Higgs boson mass in the H → γγ and H → 4l channels using the 36 fb−1 dataset.
| Author | : Mingming Yang (Ph. D.) |
| Publisher | : |
| Total Pages | : 201 |
| Release | : 2015 |
| Genre | : |
| ISBN | : |
This thesis concerns the observation of a new particle and the measurements of its properties, from the search of the Higgs boson through its decay into two photons at the CMS experiment at CERN's Large Hadron Collider (LHC), on the full LHC "Run I" data collected by the CMS detector during 2011 and 2012, consisting of proton-proton collision events at [square root of] s = 7 TeV with L = 5.1 fb-1 and at [square root of] s = 8 TeV with L = 19.7 fb-1, with the final calibration. In particular, an excess of events above the background expectation is observed, with a local significance of 5.7 standard deviations at a mass of 124.7 GeV, which constitutes the observation of a new particle through the two photon decay channel. A further measurement provides the precise mass of this new particle as 124.72+0.35 -0.36 GeV = 124.72+0.31 -0.32(stat)+0.16 -0.16(syst) GeV. Its total production cross section times two photon decay branching ratio relative to that of the Standard Model Higgs boson is determined as 1.12+0.26 -0.23 = 1.12+0.21 -0.21(stat)+0.15 -0.09(syst), compatible with the Higgs boson expectation. Further extractions of its properties relative to the Higgs boson, including the production cross section times decay branching ratios for separate Higgs production processes, couplings to bosons and to fermions, and effective couplings to the photon and to the gluon, are all compatible with the expectations for the Standard Model Higgs boson.
| Author | : [Study Group] ATLAS Collaboration CERN |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2022 |
| Genre | : |
| ISBN | : |
Abstract: A measurement of inclusive and differential fiducial cross-sections for the production of the Higgs boson decaying into two photons is performed using 139 fb−1 of proton-proton collision data recorded at s√ = 13 TeV by the ATLAS experiment at the Large Hadron Collider. The inclusive cross-section times branching ratio, in a fiducial region closely matching the experimental selection, is measured to be 67 ± 6 fb, which is in agreement with the state-of-the-art Standard Model prediction of 64 ± 4 fb. Extrapolating this result to the full phase space and correcting for the branching ratio, the total cross-section for Higgs boson production is estimated to be 58 ± 6 pb. In addition, the cross-sections in four fiducial regions sensitive to various Higgs boson production modes and differential cross-sections as a function of either one or two of several observables are measured. All the measurements are found to be in agreement with the Standard Model predictions. The measured transverse momentum distribution of the Higgs boson is used as an indirect probe of the Yukawa coupling of the Higgs boson to the bottom and charm quarks. In addition, five differential cross-section measurements are used to constrain anomalous Higgs boson couplings to vector bosons in the Standard Model effective field theory framework
| Author | : Ivan Konstantinovich Pogrebnyak |
| Publisher | : |
| Total Pages | : 322 |
| Release | : 2021 |
| Genre | : Electronic dissertations |
| ISBN | : |
This dissertation presents ATLAS measurements of the total and differential fiducial cross sections for the process of the Higgs boson production and subsequent decay to two photons. The analyzed dataset of proton-proton collisions at √s = 13 TeV has an integrated luminosity of 139 ifb and was collected during the Run 2 of the Large Hadron Collider in 2015–2018. The cross sections were measured in a fiducial phase space closely matching the experimental selection, and compared to the Standard Model predictions from the state-of-the-art calculations. The differential cross sections were measured with respect to an array of observables, allowing us to probe the kinematics, jet activity, and spin and CP properties of the Higgs boson interactions. The data were analyzed iteratively, with yearly results from partial datasets presented at conferences and in publications. The inclusive fiducial cross section obtained from the analysis of the full Run 2 dataset is 65.2 ± 4.5 (stat.) ± 5.6 (exp.) ± 0.3 (theory) fb, which is in excellent agreement with the SM prediction of 63.5 ± 3.3 fb. The results provide the state-of-the-art experimental measurements of the Higgs boson production cross sections, and extend our confidence in the SM in the Higgs sector and QCD, as well as in the computational techniques used to obtain theoretical predictions.
| Author | : David Hall |
| Publisher | : Springer |
| Total Pages | : 175 |
| Release | : 2015-06-15 |
| Genre | : Science |
| ISBN | : 3319199897 |
This thesis describes the stand-alone discovery and measurement of the Higgs boson in its decays to two W bosons using the Run-I ATLAS dataset. This is the most precise measurement of gluon-fusion Higgs boson production and is among the most significant results attained at the LHC. The thesis provides an exceptionally clear exposition on a complicated analysis performed by a large team of researchers. Aspects of the analysis performed by the author are explained in detail; these include new methods for evaluating uncertainties on the jet binning used in the analysis and for estimating the background due to associated production of a W boson and an off-shell photon. The thesis also describes a measurement of the WW cross section, an essential background to Higgs boson production. The primary motivation of the LHC was to prove or disprove the existence of the Higgs boson. In 2012, CERN announced this discovery and the resultant ATLAS publication contained three decay channels: gg, ZZ, and WW.
| Author | : Kevin Singh |
| Publisher | : |
| Total Pages | : 94 |
| Release | : 2013 |
| Genre | : |
| ISBN | : |
The Higgs decay into a photon and a Z boson, with the Z boson decaying into an electron-positron pair (electron channel) or muon-antimuon pair (muon channel), allows for accurate reconstructions of the Higgs boson mass and measurement of the Higgs to Z-[gamma] coupling. We explore selection criteria for the photon and the two leptons and provide preliminary observed and expected limits for the Higgs boson production cross section in the mass range from 120 GeV to 150 GeV. The data used in this analysis was collected with the CMS detector and corresponds to 5 fb- 1 and 19 fb-1 at center-of-mass energies of 7 TeV and 8 TeV, respectively.
| Author | : David Hall |
| Publisher | : |
| Total Pages | : |
| Release | : 2015 |
| Genre | : |
| ISBN | : 9783319199900 |
This thesis describes the stand-alone discovery and measurement of the Higgs boson in its decays to two W bosons using the Run-I ATLAS dataset. This is the most precise measurement of gluon-fusion Higgs boson production, and is among the most significant results attained at the LHC. The thesis provides an exceptionally clear exposition on a complicated analysis performed by a large team of researchers. Aspects of the analysis performed by the author are explained in detail; these include new methods for evaluating uncertainties on the jet binning used in the analysis, and for estimating the background due to associated production of a W boson and an off-shell photon. The thesis also describes a measurement of the WW cross section, an essential background to Higgs boson production. The primary motivation of the LHC was to prove or disprove the existence of the Higgs boson. In 2012, CERN announced this discovery and the resultant ATLAS publication contained three decay channels: gg, ZZ, and WW.
| Author | : Théo Megy |
| Publisher | : |
| Total Pages | : |
| Release | : 2019 |
| Genre | : |
| ISBN | : |
Abstract: The measurement of the Higgs-boson coupling to tau-leptons, based on an integrated luminosity of 36.1 ifb recorded at a centre-of-mass energy of 13 TeV by the ATLAS detector, is presented in this thesis. The analysis considers all combinations of leptonic and hadronic decays of tau-leptons, and targets the main two production modes of the Higgs boson, gluon Fusion and Vector-Boson Fusion. The inclusive cross section of the H->tautau decay channel is measured as 3.77 +1.06-0.95 (+0.60-0.59 (Stat.) +0.87-0.74 (Syst.)) pb, which corresponds to a deviation from the background-only hypothesis with an observed (expected) significance of 4.4 (4.1) standard deviations. In addition, the measurement of cross sections in the framework of Simplified Template Cross Sections is discussed. All measurement are in agreement with predictions of the Standard Model. The combined measurement of Higgs-boson properties is also presented, based on up to 79.8 ifb of data recorded at sqrt(s) = 13 TeV by the ATLAS detector. An observation of the four main production modes (ggF, VBF, VH and ttH+tH) and of four of the five main decay channels (H->gammagamma, H->ZZ, H->WW and H->bb) of the Higgs boson is achieved. In particular, the deviation from the background-only hypothesis with an observed (expected) significance of 6.5 (5.3) standard deviations for the VBF production mode is the first observation of this process by a single experiment. Measurements in the scope of the kappa-framework and of Simplified Template Cross Sections are also discussed. All the performed measurements are compatible with the Standard-Model expectations
| Author | : Théo J. Megy |
| Publisher | : |
| Total Pages | : |
| Release | : 2019 |
| Genre | : |
| ISBN | : |
Abstract: The measurement of the Higgs-boson coupling to tau-leptons, based on an integrated luminosity of 36.1 ifb recorded at a centre-of-mass energy of 13 TeV by the ATLAS detector, is presented in this thesis. The analysis considers all combinations of leptonic and hadronic decays of tau-leptons, and targets the main two production modes of the Higgs boson, gluon Fusion and Vector-Boson Fusion. The inclusive cross section of the H->tautau decay channel is measured as 3.77 +1.06-0.95 (+0.60-0.59 (Stat.) +0.87-0.74 (Syst.)) pb, which corresponds to a deviation from the background-only hypothesis with an observed (expected) significance of 4.4 (4.1) standard deviations. In addition, the measurement of cross sections in the framework of Simplified Template Cross Sections is discussed. All measurement are in agreement with predictions of the Standard Model. The combined measurement of Higgs-boson properties is also presented, based on up to 79.8 ifb of data recorded at sqrt(s) = 13 TeV by the ATLAS detector. An observation of the four main production modes (ggF, VBF, VH and ttH+tH) and of four of the five main decay channels (H->gammagamma, H->ZZ, H->WW and H->bb) of the Higgs boson is achieved. In particular, the deviation from the background-only hypothesis with an observed (expected) significance of 6.5 (5.3) standard deviations for the VBF production mode is the first observation of this process by a single experiment. Measurements in the scope of the kappa-framework and of Simplified Template Cross Sections are also discussed. All the performed measurements are compatible with the Standard-Model expectations.
