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

G. Aad 1 S. Albrand 2 J. Brown 2 J. Collot 2 S. Crépé-Renaudin 2 B. Dechenaux 2 P.A. Delsart 2 C. Gabaldon 2 M.H. Genest 2 J.Y. Hostachy 2 F. Ledroit-Guillon 2 A. Lleres 2 A. Lucotte 2 F. Malek 2 C. Monini 2 J. Stark 2 B. Trocmé 2 M. Wu 2 G. Rahal 3 S. Abdel Khalek 4 A. Bassalat 4 C. Becot 4 S. Binet 4 C. Bourdarios 4 D. Charfeddine 4 J.B. de Vivie De Regie 4 L. Duflot 4 M. Escalier 4 L. Fayard 4 D. Fournier 4 J.-F. Grivaz 4 T. Guillemin 4 F. Hariri 4 S. Henrot-Versillé 4 J. Hrivnac 4 L. Iconomidou-Fayard 4 M. Kado 4 A. Lounis 4 N. Makovec 4 L. Poggioli 4 P. Puzo 4 A. Renaud 4 D. Rousseau G. Rybkin 4 A.C. Schaffer 4 E. Scifo 4 L. Serin 4 S. Simion 4 R. Tanaka 4 H.L. Tran 4 D. Zerwas 4 Zhen Zhang 4 E.L. Gkougkousis 4 C. Nellist 4 Z. Barnovska 5 N. Berger 5 J. Colas 5 M. Delmastro 5 L. Di Ciaccio 5 S. Elles 5 C. Goy 5 T. Hryn’ova 5 S. Jézéquel 5 H. Keoshkerian 5 I. Koletsou 5 R. Lafaye 5 J. Leveque 5 V.P. Lombardo 5 N. Massol 5 P. Perrodo 5 H. Przysiezniak 5 G. Sauvage 5 E. Sauvan 5 M. Schwoerer 5 O. Simard 5 T. Todorov 5 I. Wingerter-Seez 5 L. Alio 1 M. Barbero 1 J. C. Clémens 1 Y. Coadou 1 S. Diglio 1 F. Djama 1 L. Feligioni 1 G.D. Hallewell 1 D. Hoffmann 1 F. Hubaut 1 E. B. F. G. Knoops 1 E. Le Guirriec 1 B. Li 1 D. Madaffari 1 K. Mochizuki 1 E. Monnier 1 S. Muanza 1 Y. Nagai 1 P. Pralavorio A. Rozanov 1 T. Serre 1 M. Talby 1 E. Tiouchichine 1 S. Tisserant 1 J. Toth 1 F. Touchard 1 M. Ughetto 1 L. Vacavant 1
Abstract : A measurement of spin correlation in $t\bar{t}$ 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 $t\bar{t}$ events by using the difference in azimuthal angle between the two charged leptons in the laboratory frame. In the helicity basis the measured degree of correlation corresponds to $A_{helicity} = 0.38 \pm 0.04$, 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.
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Physical Review Letters, American Physical Society, 2015, 114 (14), pp.142001. 〈10.1103/PhysRevLett.114.142001〉
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Soumis le : mardi 16 décembre 2014 - 08:14:20
Dernière modification le : mardi 13 février 2018 - 13:28:06

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G. Aad, S. Albrand, J. Brown, J. Collot, S. Crépé-Renaudin, et al.. Measurement of Spin Correlation in Top-Antitop Quark Events and Search for Top Squark Pair Production in pp Collisions at $\sqrt{s}=8$ TeV Using the ATLAS Detector. Physical Review Letters, American Physical Society, 2015, 114 (14), pp.142001. 〈10.1103/PhysRevLett.114.142001〉. 〈in2p3-01095656〉

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