Recherche et découverte du boson de Higgs avec son mode de désintégration en paire de photons avec l'expérience ATLAS au LHC : une introduction

Abstract : In the context of particle physics, within the ATLAS experiment at LHC, this document presents the discovery of a particle compatible with the Higgs boson by the combination of several decay channels, with a mass of the order of 126 GeV. With an increased statistics, that is the full set of data collected by the ATLAS experiment at LHC during the years 2011 (L=4.5\ fb^{-1} at sqrt{s}=7\ TeV) and 2012 (L=20.3 fb^{-1} at sqrt{s}=8 TeV), the particle is also discovered individually in the channel H\rightarrow\gamma\gamma with an observed significance (respectively expected) of 5.2 sigma (respectively 4.7 sigma). The analysis dedicated to the measurement of the mass (m_H) and signal strength (mu) in the channel H->gamma gamma gives the measurement : m_H = 125.98 +/- 0.42 (stat) +/- 0.28 (syst) GeV \mu = 1.29 +/- 0.30 and the constraint on the width Gamma_H of the Higgs decay of 5.0 GeV at 95 % CL. The mass combination of 2011 and 2012 campaigns for the H->gamma gamma and H-->4l channels gives the measurement : m_H=125.36 +/- 0.37 (stat) +/- 0.18 (syst) GeV The analysis dedicated to the measurement of the production modes in the channel H -> gamma gamma gives the measurements : mu_{ggF}=1.32 +/- 0.32 (stat) +0.13 - 0.09 (syst) +0.19 -0.11 (th) = 1.32 +/- 0.38 mu_{VBF}=0.8 +/- 0.7 (stat) +0.2 -0.1 (syst) +0.2 -0.3 (th) =0.8 +/- 0.7 mu_{WH} =1.0 +/- 1.5 (stat) +0.3 -0.2 (syst) +0.2 -0.1 (th) =1.0 +/- 1.6 mu_{ZH} =0.1 +3.6 -0.1 (stat) +0.7 -0.0 (syst) +0.1 -0.0 (th) =0.1 + 3.7 - 0.1 mu_{ttH} =1.6 + 2.6 -1.8 (stat) +0.6 -0.4 (syst) +0.5 -0.2 (th) = 1.6 + 2.7 - 1.8 The spin study rejects the hypothesis of spin 2 at 99 % CL. The odd parity (spin-parity 0^- state) is excluded at more than 98 % CL. Within the theoretical and experimental uncertainties accessible at the time of the analysis, all results : channels showing the excess with respect to the background only hypothesis, measured mass and signal strength, couplings, quantum numbers (J^{PC}), production modes, fiducial and differential cross-sections, are compatible with the Standard Model Higgs boson.
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Habilitation à diriger des recherches
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https://tel.archives-ouvertes.fr/tel-01161924
Contributor : Marc Escalier <>
Submitted on : Wednesday, July 17, 2019 - 11:11:01 PM
Last modification on : Sunday, July 21, 2019 - 1:11:14 AM

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Marc Escalier. Recherche et découverte du boson de Higgs avec son mode de désintégration en paire de photons avec l'expérience ATLAS au LHC : une introduction. Physique des Hautes Energies - Expérience [hep-ex]. Université Paris Sud 11, 2015. ⟨tel-01161924v2⟩

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