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

G. Aad; B. Abbott; J. Abdallah; S. Abdel Khalek; O. Abdinov; R. Aben; B. Abi; M. Abolins; O.S. AbouZeid; H. Abramowicz; Mogens Dam; Jørn Dines Hansen; Jørgen Beck Hansen; Stefania Xella; Peter Henrik Hansen; Troels Christian Petersen; Lotte Ansgaard Thomsen; Sascha Mehlhase; Morten Dam Jørgensen; Almut Maria Pingel; Ask Emil Løvschall-Jensen; Alejandro Alonso Diaz; James William Monk; Lars Egholm Pedersen; Graig Wiglesworth; Gorm Aske Gram Krohn Galster

doi:10.1103/physrevlett.114.142001

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

G. Aad, B. Abbott, J. Abdallah, S. Abdel Khalek, O. Abdinov, R. Aben, B. Abi, M. Abolins, O.S. AbouZeid, H. Abramowicz, Mogens Dam, Jørn Dines Hansen, Jørgen Beck Hansen, Stefania Xella, Peter Henrik Hansen, Troels Christian Petersen, Lotte Ansgaard Thomsen, Sascha Mehlhase, Morten Dam Jørgensen, Almut Maria PingelAsk Emil Løvschall-Jensen, Alejandro Alonso Diaz, James William Monk, Lars Egholm Pedersen, Graig Wiglesworth, Gorm Aske Gram Krohn Galster

Experimental Particle Physics

70 Citations (Scopus)

Abstract

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 language	English
Article number	142001
Journal	Physical Review Letters
Volume	114
Issue number	14
ISSN	0031-9007
DOIs	https://doi.org/10.1103/physrevlett.114.142001
Publication status	Published - 8 Apr 2015

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Aad, G., Abbott, B., Abdallah, J., Abdel Khalek, S., Abdinov, O., Aben, R., Abi, B., Abolins, M., AbouZeid, O. S., Abramowicz, H., Dam, M., Hansen, J. D., Hansen, J. B., Xella, S., Hansen, P. H., Petersen, T. C., Thomsen, L. A., Mehlhase, S., Jørgensen, M. D., ... Galster, G. A. G. K. (2015). Measurement of Spin Correlation in Top-Antitop Quark Events and Search for Top Squark Pair Production in pp Collisions at root s=8 TeV Using the ATLAS Detector. Physical Review Letters, 114(14), Article 142001. https://doi.org/10.1103/physrevlett.114.142001

Aad, G, Abbott, B, Abdallah, J, Abdel Khalek, S, Abdinov, O, Aben, R, Abi, B, Abolins, M, AbouZeid, OS, Abramowicz, H, Dam, M , Hansen, JD , Hansen, JB , Xella, S , Hansen, PH , Petersen, TC, Thomsen, LA, Mehlhase, S, Jørgensen, MD, Pingel, AM, Løvschall-Jensen, AE, Alonso Diaz, A, Monk, JW, Pedersen, LE, Wiglesworth, G & Galster, GAGK 2015, 'Measurement of Spin Correlation in Top-Antitop Quark Events and Search for Top Squark Pair Production in pp Collisions at root s=8 TeV Using the ATLAS Detector', Physical Review Letters, vol. 114, no. 14, 142001. https://doi.org/10.1103/physrevlett.114.142001

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

abstract = "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.",

author = "G. Aad and B. Abbott and J. Abdallah and {Abdel Khalek}, S. and O. Abdinov and R. Aben and B. Abi and M. Abolins and O.S. AbouZeid and H. Abramowicz and Mogens Dam and Hansen, {J{\o}rn Dines} and Hansen, {J{\o}rgen Beck} and Stefania Xella and Hansen, {Peter Henrik} and Petersen, {Troels Christian} and Thomsen, {Lotte Ansgaard} and Sascha Mehlhase and J{\o}rgensen, {Morten Dam} and Pingel, {Almut Maria} and L{\o}vschall-Jensen, {Ask Emil} and {Alonso Diaz}, Alejandro and Monk, {James William} and Pedersen, {Lars Egholm} and Graig Wiglesworth and Galster, {Gorm Aske Gram Krohn}",

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T1 - Measurement of Spin Correlation in Top-Antitop Quark Events and Search for Top Squark Pair Production in pp Collisions at root s=8 TeV Using the ATLAS Detector

AU - Aad, G.

AU - Abbott, B.

AU - Abdallah, J.

AU - Abdel Khalek, S.

AU - Abdinov, O.

AU - Aben, R.

AU - Abi, B.

AU - Abolins, M.

AU - AbouZeid, O.S.

AU - Abramowicz, H.

AU - Dam, Mogens

AU - Hansen, Jørn Dines

AU - Hansen, Jørgen Beck

AU - Xella, Stefania

AU - Hansen, Peter Henrik

AU - Petersen, Troels Christian

AU - Thomsen, Lotte Ansgaard

AU - Mehlhase, Sascha

AU - Jørgensen, Morten Dam

AU - Pingel, Almut Maria

AU - Løvschall-Jensen, Ask Emil

AU - Alonso Diaz, Alejandro

AU - Monk, James William

AU - Pedersen, Lars Egholm

AU - Wiglesworth, Graig

AU - Galster, Gorm Aske Gram Krohn

PY - 2015/4/8

Y1 - 2015/4/8

N2 - 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.

AB - 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.

U2 - 10.1103/physrevlett.114.142001

DO - 10.1103/physrevlett.114.142001

M3 - Journal article

C2 - 25910111

SN - 0031-9007

VL - 114

JO - Physical Review Letters

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IS - 14

M1 - 142001

ER -

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

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