A measurement of observables sensitive to spin correlations in tt production is presented, using 36.1 fb-1 of pp collision data at s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider. Differential cross-sections are measured in events with exactly one electron and one muon with opposite-sign electric charge as a function of the azimuthal opening angle and the absolute difference in pseudorapidity between the electron and muon candidates in the laboratory frame. The azimuthal opening angle is also measured as a function of the invariant mass of the tt system. The measured differential cross-sections are compared to predictions by several NLO Monte Carlo generators and fixed-order calculations. The observed degree of spin correlation is somewhat higher than predicted by the generators used. The data are consistent with the prediction of one of the fixed-order calculations at NLO, but agree less well with higher-order predictions. Using these leptonic observables, a search is performed for pair production of supersymmetric top squarks decaying into Standard Model top quarks and light neutralinos. Top squark masses between 170 and 230 GeV are largely excluded at the 95% confidence level for kinematically allowed values of the neutralino mass.

Aaboud, M., Aad, G., Abbott, B., Abbott, D.c., Abdinov, O., Abud, A.a., et al. (2020). Measurements of top-quark pair spin correlations in the eμ channel at √s=13 TeV using pp collisions in the ATLAS detector. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS, 80(8) [10.1140/epjc/s10052-020-8181-6].

Measurements of top-quark pair spin correlations in the eμ channel at √s=13 TeV using pp collisions in the ATLAS detector

Aielli G.;Camarri P.;Cerrito L.;De Sanctis U.;Di Ciaccio A.;Loffredo S.;
2020-01-01

Abstract

A measurement of observables sensitive to spin correlations in tt production is presented, using 36.1 fb-1 of pp collision data at s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider. Differential cross-sections are measured in events with exactly one electron and one muon with opposite-sign electric charge as a function of the azimuthal opening angle and the absolute difference in pseudorapidity between the electron and muon candidates in the laboratory frame. The azimuthal opening angle is also measured as a function of the invariant mass of the tt system. The measured differential cross-sections are compared to predictions by several NLO Monte Carlo generators and fixed-order calculations. The observed degree of spin correlation is somewhat higher than predicted by the generators used. The data are consistent with the prediction of one of the fixed-order calculations at NLO, but agree less well with higher-order predictions. Using these leptonic observables, a search is performed for pair production of supersymmetric top squarks decaying into Standard Model top quarks and light neutralinos. Top squark masses between 170 and 230 GeV are largely excluded at the 95% confidence level for kinematically allowed values of the neutralino mass.
2020
Pubblicato
Rilevanza internazionale
Articolo
Esperti anonimi
Settore FIS/01 - FISICA SPERIMENTALE
English
Con Impact Factor ISI
Aaboud, M., Aad, G., Abbott, B., Abbott, D.c., Abdinov, O., Abud, A.a., et al. (2020). Measurements of top-quark pair spin correlations in the eμ channel at √s=13 TeV using pp collisions in the ATLAS detector. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS, 80(8) [10.1140/epjc/s10052-020-8181-6].
Aaboud, M; Aad, G; Abbott, B; Abbott, Dc; Abdinov, O; Abud, Aa; Abhayasinghe, Dk; Abidi, Sh; Abouzeid, Os; Abraham, Nl; Abramowicz, H; Abreu, H; Abula...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/275859
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