Measurement of Higgs boson properties using the decay channel to b-quarks following associated production with a vector boson in $pp$ collisions at $\sqrt{s}=13$ TeV

The Higgs boson was discovered by the ATLAS and CMS experiments using the Large Hadron Collider at CERN. After the discovery, it became important to measure the properties of the Higgs boson to validate the Higgs mechanism in the Standard Model (SM). In addition, the properties of the Higgs boson such as the coupling and the differential production cross-sections are sensitive to physics beyond the Standard Model (BSM) desired from both theoretical viewpoints and cosmological observations. The Higgs boson production associated with either a $W$ or $Z$ boson ($WH$ and $ZH$) is analyzed in the $H\to b\bar{b}$ decay channel using data of $pp$ collisions at the center-of-mass energy of 13 TeV with an integrated luminosity of 139 $\text{fb}^{-1}$. In addition to increasing the data statistics, several analysis improvements are introduced. The signals are observed (expected) with the significance of 4.0 (4.1) and 5.3 (5.1) standard deviations for $WH$ and $ZH$ with respect to the background-only hypothesis, respectively. These results are strong evidence of the $WH$ production and observation of the $ZH$ production, respectively. The analysis yields signal strengths, the ratios of the observed production cross-sections times the branching ratio to the prediction of the Standard Model, for the $WH$ and $ZH$ productions as $\mu_{WH}^{bb} = 0.95^{+0.27}_{-0.25}$ and $\mu_{ZH}^{bb} = 1.08^{+0.25}_{-0.23}$, respectively. Measurement of a differential production cross-section times the branching fraction as a function of the transverse momentum of the vector boson ($p_{\mathrm{T}}^{V}$) is also performed, and the results are: $19.0\pm 12.1$ fb ($150\leq p_{\mathrm{T}}^{W} <250$ GeV), $7.2\pm 2.2$ fb ($p_{\mathrm{T}}^{W}\geq250$ GeV) for $WH$ and $42.5\pm 35.9$ fb ($75\leq p_{\mathrm{T}}^{Z}<150$ GeV), $20.5\pm 6.2$ fb ($150\leq p_{\mathrm{T}}^{Z}<250$ GeV), $5.4\pm 1.7$ fb ($p_{\mathrm{T}}^{Z}\geq250$ GeV) for $ZH$. The measured differential cross-sections are consistent with the prediction of the Standard Model within the uncertainties ranging from 85% to 30% depending on the $p_{\mathrm{T}}^{V}$ regions. The measurement of the differential cross-section of the $VH$ production sets constraints on BSM scenarios that affect the spectrum. In order to provide the experimental constraints in a model-independent way, the constraints are derived for the Wilson coefficients of dimension-6 operators in the Standard Model Effective Field Theory framework. The CP property of the $ZZH$ vertex is also studied by exploiting the $Z\to\ell^{+}\ell^{-}$ decay angles in the $ZH \to \ell^+\ell^- b\bar{b}$ channel. It is also shown that the analysis of $VH$, $H\to b\bar{b}$ significantly contributes to the global measurement of the Higgs couplings through the constraint on the total Higgs width, which is driven by the bottom Yukawa coupling.