We present first measurements of the top-quark pair-production and the
inclusive W+jets cross-section in proton-proton collisions at sqrt(s) = 7
TeV with the ATLAS detector at the Large Hadron Collider.
These are important Standard Model processes which have been
the subject of much recent theoretical attention in preparation for
In a data sample of 2.9 pb-1 we observe 37 top-pair candidates in the
single lepton and 9 in the dilepton channel, leading to the measurement
of the ttbar production cross-section
sigma(ttbar) =145 +- 31 +42 -27 pb.
In a data sample of 1.3 pb-1, cross-sections, in both the electron and
muon decay modes of the W boson, are presented as a function of jet
multiplicity and of the transverse momentum of the leading and
next-to-leading jets in the event. Measurements are also presented of
the ratio of cross sections sigam(W+ >= n) / sigma(W+ >= n-1) for
inclusive jet multiplicities n=1-4.
The measurements are compared to recent higher-order and
high-multiplicity Standard Model calculations.
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M. Mangano, M. Spiropulu, G. Unal...................Tea and Coffee will be served at 10h30