CMS-PAS-TOP-18-006

CMS-PAS-TOP-18-006
Measurement of the top quark polarization and $\mathrm{t \bar t}$ spin correlations in dilepton final states at $\sqrt{s}=$ 13 TeV
CMS Collaboration
December 2018

Abstract: Measurements of the top quark polarization and top quark pair ( $\mathrm{t \bar t}$ ) spin correlations are presented using events containing two leptons produced in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=$ 13 TeV. The data were recorded by the CMS experiment at the CERN LHC in 2016 and correspond to an integrated luminosity of 35.9 fb $^{-1}$ . A set of parton-level normalized differential cross sections, sensitive to each of the independent coefficients of the spin-dependent parts of the $\mathrm{t \bar t}$ production density matrix, is measured for the first time at $\sqrt{s}=$ 13 TeV. The measured distributions and extracted coefficients are compared with standard model predictions from Monte Carlo simulations with next-to-leading-order (NLO) accuracy in quantum chromodynamics (QCD) and from NLO QCD calculations including weak and mixed QCD-weak corrections. All measurements are found to be consistent with the expectations of the standard model, and are used in a simultaneous fit to constrain the anomalous chromomagnetic dipole moment of the top quark to $-0.07 < C_\text{tG}/\Lambda^{2} < 0.16$ TeV $^{-2}$ at 95% confidence level.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, PRD 100 (2019) 072002. The superseded preliminary plots can be found here.

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