Evidence for spin correlation in tt production

• Published in: Physical review letters Vol. 108; no. 3
• Main Author: Abazov, Victor Mukhamedovich
• Format: Journal Article
• Language: English
• Published: United States American Physical Society (APS) 19-01-2012
• Subjects: A CENTERS; Experiment-HEP; FERMILAB TEVATRON; LEPTONS; LUMINOSITY; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; PRODUCTION; SPIN; STANDARD MODEL
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.108.032004

We present a measurement of the ratio of events with correlated t and t spins to the total number of tt events. This ratio f is evaluated using a matrix-element-based approach in 729 tt candidate events with a single lepton ℓ (electron or muon) and at least four jets. The analyzed pp collisions data correspond to an integrated luminosity of 5.3 fb-1 and were collected with the D0 detector at the Fermilab Tevatron collider operating at a center-of-mass energy \(\sqrt{s}=1.96\) TeV. Combining this result with a recent measurement of f in dileptonic final states, we find f in agreement with the standard model. In addition, the combination provides evidence for the presence of spin correlation in tt events with a significance of more than 3 standard deviations.