Measurement of spin correlation in tt¯ 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¯→W+bW−b¯→ℓ+νbℓ−ν¯b¯ final states produced in pp¯ 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.