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  • PhysRevLett.108.212001

    Rights statement: Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. © 2012 CERN, for the ATLAS Collaboration

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Observation of Spin Correlation in tt¯ Events from pp Collisions at s√=7  TeV Using the ATLAS Detector

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Article number212001
<mark>Journal publication date</mark>24/05/2012
<mark>Journal</mark>Physical review letters
Issue number21
Volume108
Number of pages19
Publication StatusPublished
<mark>Original language</mark>English

Abstract

A measurement of spin correlation in tt¯ production is reported using data collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 2.1  fb−1. Candidate events are selected in the dilepton topology with large missing transverse energy and at least two jets. The difference in azimuthal angle between the two charged leptons in the laboratory frame is used to extract the correlation between the top and antitop quark spins. In the helicity basis the measured degree of correlation corresponds to Ahelicity=0.40+0.09−0.08, in agreement with the next-to-leading-order standard model prediction. The hypothesis of zero spin correlation is excluded at 5.1 standard deviations.

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Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. © 2012 CERN, for the ATLAS Collaboration