Measurement of Spin Correlations in Top Pair Events in the Dilepton Channels in pp Collisions at 7 TeV

We present a measurement of the top spin correlation in top-antitop pair production in the dilepton channels in pp collisions at 7 TeV. The data sample used for the measurement corresponds to an integrated luminosity of 5.0 fb$^{-1}$ collected with the CMS detector at the LHC. The measurement is performed in events with two leptons (electrons or muons) in the final state, and at least two jets where at least one is identified as a b-jet. In addition the presence of missing transverse energy is required. The spin correlation in top-antitop pair events is extracted from a fit to the angular distribution between the two selected leptons. In the helicity basis, the correlation coefficient is found to be $0.24 \pm 0.02 \pm 0.08$. The spin correlation is also investigated through other variables, for different top-antitop pair invariant masses. All measurements are found to be in agreement with the Standard Model predictions.