Abstract
We perform global fits of the Higgs boson couplings to all the 7 TeV, 8 TeV, and 13 TeV data available up to the Summer 2018. New measurements at 13 TeV extend to include the Higgs signal strengths exclusively measured in associated Higgs production with top-quark pair and the third-generation Yukawa couplings now have been established. Some important consequences emerge from the global fits. (i) The overall average signal strength of the Higgs boson stands at 2σ above the SM value (μ = 1.10 ± 0.05). (ii) For the first time the bottom-quark Yukawa coupling shows a preference of the positive sign to the negative one. (iii) The negative top-quark Yukawa coupling is completely ruled out unless there exist additional particles running in the H-γ-γ loop with contributions equal to two times the SM top-quark contribution within about 10 %. (iv) The branching ratio for nonstandard decays of the Higgs boson is now below 8.4% at the 95% confidence level.
Highlights
Some important consequences emerge from the global fits. (i) The overall average signal strength of the Higgs boson stands at 2σ above the SM value (μ = 1.10 ± 0.05). (ii) For the first time the bottom-quark Yukawa coupling shows a preference of the positive sign to the negative one. (iii) The negative top-quark Yukawa coupling is completely ruled out unless there exist additional particles running in the H-γ-γ loop with contributions equal to two times the SM top-quark contribution within about 10 %. (iv) The branching ratio for nonstandard decays of the Higgs boson is below 8.4% at the 95% confidence level
Signal strengths measured at the Tevatron [12, 13] and, for the Higgs-boson data at 7 and 8 TeV, we use 20 signal strengths and the correlation matrix obtained in the combined ATLAS and CMS analysis [11]
The data precision is sensitive to the bottom-Yukawa coupling and the overall average signal strength shows a 2-σ deviation from the SM value
Summary
In order to make the current presentation more self-contained, we include here brief description of the formalism that we use in calculating the signal strengths and chi-squares. Higgs couplings to two photons: the amplitude for the decay process H → γγ can be written as. Including some additional loop contributions from new particles, the scalar and pseudoscalar form factors, retaining only the dominant loop contributions from the third-generation fermions and W ±, are given by. Higgs couplings to two gluons: similar to H → γγ, the amplitude for the decay process H → gg can be written as. The decay rate of H → gg is proportional to |Sg|2 + |P g|2.3 Again, including some additional loop contributions from new particles, the scalar and pseudoscalar form factors are given by. Where Q denote the experimentally defined channel involved with the decay D and the decomposition coefficients CQP may depend on the relative Higgs production cross sections for a given Higgs-boson mass, experimental cuts, etc. Μpcormodbined 1.11+−00..0077 1.02+−00..1188 1.15+−00..2109 1.19+−00..3320 0.93+−00..2244 1.16+−00..2222 1.10+−00..0066
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