Search for the Standard Model Higgs boson produced in association with vector bosons and decaying to $b\bar{b}$ using the ATLAS detector

A new neutral boson decaying into pairs of photons and W or Z bosons with an invariant mass of ~ 125 GeV has been observed and requires confirmation of its coupling to fermions in order to determine whether it is the Standard Model (SM) Higgs boson. A vital observation would be its decay into $b$ quark pairs, which has a predicted branching ratio of 58% for $m_{H}$ = 125 GeV. This poster presents an updated direct search with the ATLAS experiment for $b\bar{b}$ decays of the Standard Model Higgs boson produced in association with a W or Z boson using 4.7 and 20.3 fb-1 of LHC proton-proton data at centre-of-mass energies of 7 and 8 TeV, respectively. The search is performed in the three decay modes $ZH \rightarrow \nu\nu b\bar{b}$, $WH \rightarrow \ell\nu b\bar{b}$ and $ZH \rightarrow \ell\ell b\bar{b}$ with $\ell$ denoting either electrons or muons. No significant excess is observed. The observed (expected) 95% C.L. upper limit on the production cross section times the $pp \rightarrow (W/Z)(H \rightarrow b\bar{b})$ branching ratio for $m_{H}$ = 125 GeV is found to be 1.4 (1.3) times the SM prediction. The diboson $(W/Z)Z$ production with $Z \rightarrow b\bar{b}$ is used to validate the analysis. The ratio of the observed Higgs (diboson) cross section to the SM expectation is found to be $\mu = 0.2 \pm 0.5 (stat.) \pm 0.4 (syst.) (\mu_{VZ} = 0.9 \pm 0.2)$.