Search for ttH(H to bb)

For a light Higgs boson, with mH ≤ 135 GeV, the largest decay mode is H to bb. Events where the Higgs boson is produced in association with a tt pair manifest a distinct signature due to the presence of two W bosons and four b quarks. Topological and kinematical quantities are used to reconstruct the tt system. The identification of an additional bb pair from the Higgs boson decay is used to further reduce the background. In this analysis we focus on the sensitivity to a light Standard Model Higgs boson with the ATLAS detector in the channel ttH(H → bb) using the semi-leptonic final state with 30fb−1 of integrated luminosity. The relevant backgrounds to the channel are investigated and the impact of their associated systematic uncertainties is explored.