Measurement of spin correlation in tt̄ 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 t ¯ t → W + bW − ¯ b → ℓ + νbℓ − ¯ ν ¯ b final states produced in p¯ p 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 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.