Measurement of Spin Correlation in Top-Antitop Quark Events and Search for Top Squark Pair Production in pp Collisions at √s =8 TeV Using the ATLAS Detector

ATLAS Collaboration

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A measurement of spin correlation in tt¯ production is presented using data collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb-1. The correlation between the top and antitop quark spins is extracted from dilepton tt¯ events by using the difference in the azimuthal angle between the two charged leptons in the laboratory frame. In the helicity basis the measured degree of correlation corresponds to Ahelicity=0.38±0.04, in agreement with the standard model prediction. A search is performed for pair production of top squarks with masses close to the top quark mass decaying to predominantly right-handed top quarks and a light neutralino, the lightest supersymmetric particle. Top squarks with masses between the top quark mass and 191 GeV are excluded at the 95% confidence level.

Original languageEnglish
Article number142001
JournalPhysical Review Letters
Issue number14
StatePublished - 8 Apr 2015


FundersFunder number
Not addedST/N000420/1
National Science Foundation1119200, 1506173
Seventh Framework Programme246806
Science and Technology Facilities CouncilST/L001195/1, ST/J00474X/1, ST/M004821/1, ST/I005846/1, ST/M002306/1, ST/J004928/1, ST/K001361/1, ST/K003666/1, ST/L003414/1, GRIDPP, ST/L005662/1, ST/K001310/1, ST/L006464/1, ST/J00488X/1, ST/M503575/1, ST/J501074/1, ST/L001144/1, ST/L003112/1, ST/J005525/1, ST/M001504/1, ST/K001248/1, ST/L003325/1, ST/I000178/1, ST/G50228X/1, ST/H001093/2, ST/M001431/1, ST/K001418/1, ST/K001302/1, ST/K001388/1, ST/K001329/1, ST/K50208X/1, ST/L001179/1, ST/I005803/1, ST/J004944/1, ST/M001407/1, ST/I006080/1, ST/L006480/1, ST/I000186/1, ST/M006980/1, ST/G502320/1, ST/M001733/1, ST/M006417/1, PP/D002915/1, ST/M000664/1, ST/H00100X/1, ST/L000970/1, ST/H00100X/2, ST/K000705/1, ST/L003511/1, PP/E003087/1, ST/N000307/1, PP/E000355/1, ST/M001474/1, ST/I00372X/1, PP/E002846/1, ST/K003658/1, ST/J005487/1, ST/I006056/1, ST/M003213/1, PP/E000444/1, ST/K00137X/1, ST/N000277/1, ST/J005576/1
Japan Society for the Promotion of Science23104005
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung156083, 149246


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