Spin Correlation and W Helicity in Top Events with ATLAS

In 7 TeV proton - proton collisions at the LHC, pairs of top and anti-top quarks are expected to be mostly produced through gluon fusion, in contrast to production at the Tevatron, where quark annihilation dominates. The ATLAS experiment has now recorded a large number of top quark pairs, allowing this domain to be explored in detail. We present measurements of the spin correlation between top and anti-top quarks. The helicity fractions of W bosons from top quark decays are precisely predicted by the Standard Model and a deviation could reveal the presence of new physics. We also present a measurement of the W helicity fractions from top quark decays in ATLAS.