Abstract

Combined measurements of Higgs boson production cross sections and branching fractions are presented. The combination is based on the analyses of the Higgs boson decay modes $H \to \gamma\gamma$, $ZZ^\ast$, $WW^\ast$, $\tau\tau$, $b\bar{b}$, $\mu\mu$, searches for decays into invisible final states, and on measurements of off-shell Higgs boson production. Up to $79.8$ fb$^{-1}$ of proton-proton collision data collected at $\sqrt{s}=$ 13 TeV with the ATLAS detector are used. Results are presented for the gluon-gluon fusion and vector-boson fusion processes, and for associated production with vector bosons or top-quarks. The global signal strength is determined to be $\mu = 1.11^{+0.09}_{-0.08}$. The combined measurement yields an observed (expected) significance for the vector-boson fusion production process of $6.5\sigma$ ($5.3\sigma$). Measurements in kinematic regions defined within the simplified template cross section framework are also shown. The results are interpreted in terms of modifiers applied to the Standard Model couplings of the Higgs boson to other particles, and are used to set exclusion limits on parameters in two-Higgs-doublet models and in the simplified Minimal Supersymmetric Standard Model. No significant deviations from Standard Model predictions are observed.

Highlights

  • Following the discovery of the Higgs boson H [1–6] by the ATLAS [7] and CMS [8] experiments, its properties have been probed using proton–proton collision data produced by the Large Hadron Collider (LHC) at CERN

  • The inelastic pp collisions were simulated with PYTHIA8 using the MSTW2008LO [120] set of parton distribution functions (PDFs) with the A2 [121] set of tuned parameters or using the NNPDF2.3LO set of PDFs with the A3 [122] set of tuned parameters

  • Searches for decays of the Higgs boson into invisible final states select events with large missing transverse momentum; backgrounds are suppressed by requiring in addition either jets with a vector-boson fusion (VBF) topology [21], an associated Z boson decaying into charged leptons [22] or an associated W or Z boson decaying into hadronic final states [23]

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Summary

INTRODUCTION

Following the discovery of the Higgs boson H [1–6] by the ATLAS [7] and CMS [8] experiments, its properties have been probed using proton–proton (pp) collision data produced by the Large Hadron Collider (LHC) at CERN. In the weak vector-boson fusion (VBF) production process [17]; associated production with a top–antitop pair (ttH) [12,18,19]; the H → μμ decay channel following the same methodology as presented in Ref. All the input analyses except those for the H → μμ and the VBF, H → bbprocesses use a parametrization of the Higgs boson signal yields based on the Stage 1 simplified template cross section (STXS) framework [35,36] described in Sec. VI A. The paper is structured as follows: Section II describes the data and simulation samples and Sec. III presents the analyses in individual decay channels which are used as inputs to the combination. Measurements of cross sections times branching fractions for Higgs boson production and decay processes are shown in Sec. V C.

DATA AND SIMULATED EVENT SAMPLES
INDIVIDUAL CHANNEL MEASUREMENTS
Searches for invisible Higgs boson decays
Off-shell Higgs boson production
STATISTICAL MODEL
Global signal strength
Production cross sections
Products of production cross sections and branching fractions
Ratios of cross sections and branching fractions
Simplified template cross section framework
Results
INTERPRETATION OF RESULTS IN THE κ FRAMEWORK
Framework for coupling-strength measurements
Fermion and gauge boson couplings
Probing BSM contributions in loops and decays
Result
Generic parametrization assuming no new particles in loops and decays
Generic parametrization using ratios of coupling modifiers
VIII. CONSTRAINTS ON NEW PHENOMENA
Two-Higgs-doublet model
Simplified minimal supersymmetric Standard Model
CONCLUSIONS

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