Observation of spin correlation in ttbar events from pp collisions at sqrt(s) = 7 TeV using the ATLAS detector

G. Aad; Nele Maria Philomena Boelaert; Mogens Dam; Jørgen Beck Hansen; Peter Henrik Hansen; Jørn Dines Hansen; John Renner Hansen; Simon Johann Franz Heisterkamp; Morten Dam Jørgensen; Esben Bryndt Klinkby; Björn Stefan Nilsson; Sascha Mehlhase; Troels Christian Petersen; Stefania Xella

doi:10.1103/PhysRevLett.108.212001

Observation of spin correlation in ttbar events from pp collisions at sqrt(s) = 7 TeV using the ATLAS detector

G. Aad, Nele Maria Philomena Boelaert, Mogens Dam, Jørgen Beck Hansen, Peter Henrik Hansen, Jørn Dines Hansen, John Renner Hansen, Simon Johann Franz Heisterkamp, Morten Dam Jørgensen, Esben Bryndt Klinkby, Björn Stefan Nilsson, Sascha Mehlhase, Troels Christian Petersen, Stefania Xella

72 Citations (Scopus)

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 2.1fb^-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 A_helicity=0.40 min 0.08 plus 0.09, in agreement with the next-to-leading-order standard model prediction. The hypothesis of zero spin correlation is excluded at 5.1 standard deviations.

Original language	English
Journal	Physical Review Letters
Volume	108
Issue number	21
Pages (from-to)	212001
Number of pages	19
ISSN	0031-9007
DOIs	https://doi.org/10.1103/PhysRevLett.108.212001
Publication status	Published - 24 May 2012

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Aad, G., Boelaert, N. M. P., Dam, M., Hansen, J. B., Hansen, P. H., Hansen, J. D., Hansen, J. R., Heisterkamp, S. J. F., Jørgensen, M. D., Klinkby, E. B., Nilsson, B. S., Mehlhase, S., Petersen, T. C., & Xella, S. (2012). Observation of spin correlation in ttbar events from pp collisions at sqrt(s) = 7 TeV using the ATLAS detector. Physical Review Letters, 108(21), 212001. https://doi.org/10.1103/PhysRevLett.108.212001

Aad, G, Boelaert, NMP, Dam, M , Hansen, JB , Hansen, PH , Hansen, JD , Hansen, JR, Heisterkamp, SJF, Jørgensen, MD, Klinkby, EB, Nilsson, BS, Mehlhase, S, Petersen, TC & Xella, S 2012, 'Observation of spin correlation in ttbar events from pp collisions at sqrt(s) = 7 TeV using the ATLAS detector', Physical Review Letters, vol. 108, no. 21, pp. 212001. https://doi.org/10.1103/PhysRevLett.108.212001

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title = "Observation of spin correlation in ttbar events from pp collisions at sqrt(s) = 7 TeV using the ATLAS detector",

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 2.1fb-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 min 0.08 plus 0.09, 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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doi = "10.1103/PhysRevLett.108.212001",

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T1 - Observation of spin correlation in ttbar events from pp collisions at sqrt(s) = 7 TeV using the ATLAS detector

AU - Aad, G.

AU - Boelaert, Nele Maria Philomena

AU - Dam, Mogens

AU - Hansen, Jørgen Beck

AU - Hansen, Peter Henrik

AU - Hansen, Jørn Dines

AU - Hansen, John Renner

AU - Heisterkamp, Simon Johann Franz

AU - Jørgensen, Morten Dam

AU - Klinkby, Esben Bryndt

AU - Nilsson, Björn Stefan

AU - Mehlhase, Sascha

AU - Petersen, Troels Christian

AU - Xella, Stefania

PY - 2012/5/24

Y1 - 2012/5/24

N2 - 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 2.1fb-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 min 0.08 plus 0.09, in agreement with the next-to-leading-order standard model prediction. The hypothesis of zero spin correlation is excluded at 5.1 standard deviations.

AB - 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 2.1fb-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 min 0.08 plus 0.09, in agreement with the next-to-leading-order standard model prediction. The hypothesis of zero spin correlation is excluded at 5.1 standard deviations.

U2 - 10.1103/PhysRevLett.108.212001

DO - 10.1103/PhysRevLett.108.212001

M3 - Journal article

C2 - 23003244

SN - 0031-9007

VL - 108

SP - 212001

JO - Physical Review Letters

JF - Physical Review Letters

IS - 21

ER -

Observation of spin correlation in ttbar events from pp collisions at sqrt(s) = 7 TeV using the ATLAS detector

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