Combination of Higgs boson measurements at $\sqrt{s} =$ 13 TeV and their interpretations by the ATLAS experiment

Abstract

This paper presents combined measurements of Higgs boson production and decay using up to 140 fb$^{-1}$ of proton--proton collision data collected by the ATLAS experiment at the LHC at $\sqrt{s} = 13$ TeV. The inclusive Higgs boson event rate relative to its Standard Model prediction is determined to be $0.990 ^{+0.053}_{-0.051} = 0.990 \pm 0.027 \text{ (stat.) } \pm 0.024 \text{ (exp.) } ^{+0.037}_{-0.035} \text{ (sig. theo.) } ^{+0.016}_{-0.015} \text{ (bkg. theo.)}$, separating statistical, experimental, signal-theory and background-theory uncertainty components. The signal theory uncertainty is the largest contribution, dominated by missing higher-order terms in QCD and the modelling of parton shower effects. Inclusive production cross-sections and decay branching ratios are measured, with sensitivities improved by up to 35% relative to the previous ATLAS publication. Production cross-sections for individual decay channels are also reported. The results are interpreted in terms of modifiers to Higgs boson couplings. The combination of single Higgs boson and Higgs boson pair production measurements yields $κ_λ= 1.3^{+3.1}_{-1.6}$ for the modifier to the Higgs boson self-coupling, with an interval of $[-1.5, 6.5]$ at 95% confidence level. The partial width in the $H\to b\bar{b}$ decay channel is used to obtain the first ATLAS determination of the running mass of the $b$-quark at the Higgs boson mass scale in the modified minimal subtraction scheme, found to be $m_b(m_H) = 2.73^{+0.27}_{-0.25}$ GeV. The total width of the Higgs boson is measured to be $Γ_H = 3.6^{+2.1}_{-1.6}$ MeV based on its on- and off-shell production rates. The kinematics of Higgs boson production are probed within the framework of Simplified Template Cross-sections in 44 kinematic regions, and the results are interpreted in the context of Standard Model Effective Field Theory models.