  A search for the Standard Model Higgs boson at the Large Hadron Collider
(LHC) running at a centre-of-mass energy of 7 TeV is reported, based on a total
integrated luminosity of up to 40 pb^-1 collected by the ATLAS detector in
2010. Several Higgs boson decay channels: H -> {\gamma}{\gamma}, H -> ZZ (*) ->
llll, H -> ZZ -> ll{\nu}{\nu}, H -> ZZ -> llqq, H -> W W (*) -> l{\nu}l{\nu}
and H -> W W -> l{\nu}qq (l is e, {\mu}) are combined in a mass range from 110
GeV to 600 GeV. The highest sensitivity is achieved in the mass range between
160 GeV and 170 GeV, where the expected 95% CL exclusion sensitivity is at
Higgs boson production cross sections 2.3 times the Standard Model prediction.
Upper limits on the cross section for its production are determined. Models
with a fourth generation of heavy leptons and quarks with Standard Model-like
couplings to the Higgs boson are also investigated and are excluded for a Higgs
boson mass in the range from 140 GeV to 185 GeV.
