Search for the bb decay of the Standard Model Higgs boson in associated W/ZH production with the ATLAS detector

A search for the bb decay of the Standard Model Higgs boson is performed with the ATLAS experiment using the full dataset recorded at the LHC in Run 1. The integrated luminosities used from pp collisions at √s = 7 and 8 TeV are 4.7 and 20.3 fb−1, respectively. The processes considered are associated (W/Z)H production, with W → lν, Z → ll (l = e, μ), and Z → νν. No significant excess is observed above the Standard Model (SM) backgrounds. For mH=125 GeV, a 95% CL upper limit of 1.4 times the SM expectation is set on the cross section times branching ratio for pp → (W/Z)(H → bb). The corresponding limit expected in the absence of signal is 1.3. The ratio of the measured signal strength to the SM expectation is found to be μ = 0.2 ± 0.5(stat.) ± 0.4(syst.). The analysis procedure is validated by a measurement of the yield of (W/Z)Z production, with Z → bb, from which the ratio of the observed signal strength to the SM expectation is found to be μVZ =0.9±0.2.