Measurement of spin correlation in ttbar production using dilepton final states

TL;DR

This paper measures the spin correlation between top and anti-top quarks in proton-antiproton collisions, using dilepton final states, and finds results consistent with both the Standard Model prediction and no correlation.

Contribution

First measurement of top-antitop spin correlation in dilepton final states at the Tevatron, using angular distributions to extract correlation strength.

Findings

Measured correlation strength C=0.10^{+0.45}_{-0.45}

Results agree with NLO QCD predictions within two standard deviations

Results also compatible with no spin correlation hypothesis

Abstract

We measure the correlation between the spin of the top quark and the spin of the anti-top quark in (ttbar -> W+ W- b bbar -> l+ nu b l- nubar bbar) final states produced in ppbar collisions at a center of mass energy sqrt(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 tbar 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.