Abstract

Combined analyses of the Higgs boson production and decay rates as well as its coupling strengths to vector bosons and fermions are presented. The combinations include the results of the analyses of the Hrightarrow gamma gamma ,, ZZ^*,, WW^*,, Zgamma ,, bbar{b},, tau tau and mu mu decay modes, and the constraints on the associated production with a pair of top quarks and on the off-shell coupling strengths of the Higgs boson. The results are based on the LHC proton-proton collision datasets, with integrated luminosities of up to 4.7 mathrm {fb}^{-1} at sqrt{s}=7 TeV and 20.3 mathrm {fb}^{-1} at sqrt{s}=8 TeV, recorded by the ATLAS detector in 2011 and 2012. Combining all production modes and decay channels, the measured signal yield, normalised to the Standard Model expectation, is 1.18^{+0.15}_{-0.14}. The observed Higgs boson production and decay rates are interpreted in a leading-order coupling framework, exploring a wide range of benchmark coupling models both with and without assumptions on the Higgs boson width and on the Standard Model particle content in loop processes. The data are found to be compatible with the Standard Model expectations for a Higgs boson at a mass of 125.36 GeV for all models considered.

Highlights

  • Higgs boson can be precisely calculated once the mass is known

  • The Higgs boson transverse momentum distribution from ggF production is reweighted to match the calculation of HRes2.1 [90,91], which includes QCD corrections up to the next-to-nextto-leading order (NNLO) and next-to-next-to-leading logarithm (NNLL) in perturbative expansions

  • Components of theoretical uncertainties, scale uncertainties of a given Higgs boson production process as well as PDF-induced uncertainties, that affect the inclusive signal rate are described with common nuisance parameters in all channels, whereas components of theoretical uncertainties that affect the acceptance of individual channels are modelled with separate nuisance parameters for each decay channel

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Summary

Introduction

Higgs boson can be precisely calculated once the mass is known. precision measurements of the properties of the new particle are critical in ascertaining whether the newly discovered particle is fully responsible for EWSB and whether there are potential deviations from SM predictions. Contributions are expected from bb → H (bbH ) and production in association with a single top quark (t H ). The latter proceeds through either the qb → t H q or gb → W t H process. The LHC is expected to be most sensitive to the Higgs boson decays of H → γ γ , Z Z ∗, W W ∗, τ τ and bb. Together they account for approximately 88 % of all decays of a SM Higgs boson at m H ∼ 125 GeV. These results are based on the full proton-proton collision data with integrated luminosities of up to 4.7 fb−1

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Input analyses to the combinations
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Off-shell Higgs boson production
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Statistical procedure
Signal-strength measurements
Global signal strength
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Individual production processes
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Boson and fermion-mediated production processes
Ratios of production cross sections and partial decay widths
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Framework for coupling-strength measurements
Characterisation of the input measurements in terms of coupling strengths
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Effective coupling-strength scale factors
Strategies for measurements of absolute coupling strengths
Assuming only SM contributions to the total width
Standard Model
Allowing for invisible or undetected Higgs boson decays in the total width
No assumption about the total width
Probing relations within the fermion coupling sector
Probing the up- and down-type fermion symmetry
Probing the quark and lepton symmetry
Probing BSM contributions in loop vertices only
Probing BSM contributions in loop vertices and to the total width
Generic models
Generic model 1: no new particles in loops and in decays
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Generic model 2: allow new particles in loops and in decay
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Conclusion
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Findings
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