Abstract
One year ago, a new particle with the mass of 125 GeV and properties expected for the Standard Model Higgs boson was discovered by ATLAS and CMS experiments at the Large Hadron Collider at CERN in proton-proton collisions at center-of-mass energies √s = 7 TeV and 8 TeV. Since that time more data at 8 TeV were accumulated and analyzed and a progress was reached in the measurement of the particle properties. In this note an overview of Higgs boson results obtained recently at ATLAS experiment is given. Complete dataset which corresponds to 4.7 fb−1 (20.5 fb−1) of the data obtained at √s = 7 TeV (8 TeV) collisions, respectively, is used. The following four signal decay channels are considered: H → γγ, H → ZZ* → 4ℓ, H → WW* → ℓℓνν and H → bb¯. These channels together with H → ττ channel are combined to extract Higgs boson mass, strength, coupling constants, spin and parity. All experimental results are compatible with the Standard Model predictions.
Highlights
The search for the Standard Model (SM) Higgs boson (H) at the Large Hadron Collider (LHC) [1] is known to be complicated task as expected signal production cross section is σH =O(10) pb while background rates are much high√er
Results of statistical combinations of the H → γγ, H → ZZ⋆ → llll and H → WW ⋆ → llνν decay channels are published in Ref.[7] and Ref.[8]; in some cases preliminary results from Ref.[17] are presented in the note including H → ττ and H → bb
Based on analysis of H → γγ, H → ZZ⋆ → llll, H → WW ⋆ → llνν decay channels in complete dataset taken at 7 TeV and 8 TeV together with H → bband H → ττ channels at 7 TeV only, the ATLAS experiment discovered a neutral boson with a mass ≈125 GeV having a production cross section compatible with the SM Higgs boson; fermionic decay modes of this boson are not yet discovered;
Summary
The search for the Standard Model (SM) Higgs boson (H) at the Large Hadron Collider (LHC) [1] is known to be complicated task as expected signal production cross section is σH =O(10) pb while background rates are much high√er. ΣH × BR(H → llll) is only a few pb due to the small leptonic branching ratio of the Z boson Despite all these difficulties, both the ATLAS [3] and CMS [4] Collaborations at the LHC were able to discover one year ago a new particle with the properties of a SM-like Higgs boson combining the H → γγ, H → ZZ⋆ → llll, H → WW ⋆ → llνν, H → bband H → ττ decay channels. Both the ATLAS [3] and CMS [4] Collaborations at the LHC were able to discover one year ago a new particle with the properties of a SM-like Higgs boson combining the H → γγ, H → ZZ⋆ → llll, H → WW ⋆ → llνν, H → bband H → ττ decay channels Their studies were based on the complete data taken at 7 TeV (≈5 fb−1) and on one third of the 8-TeV dataset (≈6 fb−1). Aste√pasra=te8cToenVtrifbourttihoensmforosmt prdoimffeisreinngt production mechanisms as function decay channels X as function of mH of mH [2]
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