The search for the Standard Model Higgs boson produced in association with a vector boson and decaying to bottom quarks with the ATLAS detector

SUPA - School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom

^a e-mail: P.J.Clark@ed.ac.uk

Abstract

These proceedings present an updated search for the Standard Model Higgs boson produced in association with a W or Z boson and decaying to bb̅. The analysis uses 4.7 fb⁻¹ of LHC proton-proton collision data at √s = 7 TeV and 13.0 fb⁻¹ at √s = 8 TeV recorded by the ATLAS experiment. The search is performed using events containing zero, one or two electrons or muons targeting the decay modes ZH → νν̅bb, WH → ℓνbb̅ and ZH → ℓ⁺ℓ^νbb̅. No significant excess is observed. For m_H = 125 GeV, the observed (expected) upper 95% confidence level limit on the cross section times the branching ratio is 1.8 (1.9) times the Standard Model prediction. A Standard Model Higgs boson with m_H = 110 GeV is excluded. As a validation of the analysis method, the production of diboson pairs, WZ and ZZ, with a Z boson decaying to bb̅, has been observed with a significance of 4.0 standard deviations and a rate compatible with the Standard Model expectation. A search was also made in the tt̅H channel using 4.7 fb⁻¹ of LHC data at √s = 7 TeV, focusing on the semileptonic decay mode of the tt̅ system. For a Higgs boson with m_H = 125 GeV, the observed (expected) upper 95% confidence level limit is 13.1 (10.5) times the Standard Model using tt̅H.