Observation of H→bb¯ decays and VH production with the ATLAS detector

A search for the decay of the Standard Model Higgs boson into a $b\overline{b}$ pair when produced in association with a W or Z boson is performed with the ATLAS detector. The data, corresponding to an integrated luminosity of $79.8{\mathrm{fb}}^{-1}$ were collected in proton–proton collisions during Run 2 of the Large Hadron Collider at a centre-of-mass energy of $13\text{TeV}$. For a Higgs boson mass of $125\text{GeV}$, an excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.9 (4.3) standard deviations. A combination with the results from other searches in Run 1 and in Run 2 for the Higgs boson in the $b\overline{b}$ decay mode is performed, which yields an observed (expected) significance of 5.4 (5.5) standard deviations, thus providing direct observation of the Higgs boson decay into b-quarks. The ratio of the measured event yield for a Higgs boson decaying into $b\overline{b}$ to the Standard Model expectation is $1.01\pm 0.12{(\mathrm{stat}.)}_{-0.15}^{+0.16}(\mathrm{syst}.)$. Additionally, a combination of Run 2 results searching for the Higgs boson produced in association with a vector boson yields an observed (expected) significance of 5.3 (4.8) standard deviations.