Measurement of spin correlation in tt-bar production using dilepton final states

We measure the correlation between the spin of the top quark and the spin of the anti-top quark in tt-bar→W+bW-b-bar→l+νbl-ν-bar b-bar final states produced in pp-bar collisions at a center of mass energy √(s)=1.96 TeV, where l is an electron or muon. The data correspond to an integrated luminosity of 5.4 fb-1 and were collected with the D0 detector at the Fermilab Tevatron collider. The correlation is extracted from the angles of the two leptons in the t and t-bar rest frames, yielding a correlation strength C=0.10-0.45+0.45, in agreement with the NLO QCD prediction within two standard deviations, but also in agreement with the no correlation hypothesis.