Measurement of ttbar Helicity Fractions and Spin Correlation in ppbarCollisions at sqrt{s} = 1.96 TeV.

[摘要] In the production of top-antitop quark pairs during proton-antiproton collisions, the spins of the top and antitop are correlated. This correlation is quantifed by the spin correlation coefficient kappa or the fraction of top quarks produced with opposite helicity FOH, whichare determined by the QCD interaction mechanism that produces top-antitop pairs. A deviationof the correlation from the predicted value could be an indication of new production mechanisms. We describe a measurement of the top-antitop spin correlation using the lepton plus jets decay channel, where the decay proceeds via ttbar to (W+ b)(W- bbar) to (q q;; b)(l nu bbar) or (l nu b)(q q;; bbar), in data corresponding to 4.3 fb-1 of integrated luminosity collected with the CDF detector. In the helicity basis, we find an opposite helicity fraction FOH = 0.80 +/- 0.25 (stat) +/- 0.08 (syst) and a spin correlation coefficient kappa = 0.60 +/- 0.50 (stat) +/- 0.16 (syst), which are in good agreement with the theoretical predictions FOH = 0.70 and kappa = 0.40.

[发布机构] University of Michigan

[效力级别] Top Quark Helicity

[关键词] Top Quark Spin;Top Quark Helicity;Top Quark Spin Correlation;Physics;Science;Physics