CMS-PAS-TOP-14-023

CMS-PAS-TOP-14-023
Measurements of $ \mathrm{ t \bar{t} } $ spin correlations and top-quark polarization using dilepton final states in pp collisions at $ \sqrt{s} = $ 8 TeV
CMS Collaboration
September 2015

Abstract: Spin correlations and polarization are measured in top quark-antiquark pairs produced in pp collisions at the LHC at $ \sqrt{s} =$ 8 TeV. The data correspond to an integrated luminosity of 19.5 fb$^{-1}$ collected with the CMS detector. The measurements are performed using events with two oppositely charged leptons (electrons or muons) and two or more jets, where at least one of the jets is identified as originating from a b quark. The spin correlations and polarization are measured from the angular distributions of the two selected leptons, unfolded to the parton level, both inclusively and differentially with respect to the invariant mass, rapidity, and transverse momentum of the $ \mathrm{ t \bar{t} } $ system. All measurements are found to be in agreement with predictions of the standard model of particle physics. A search for new physics in the form of a top quark chromo-magnetic anomalous coupling is performed, and the measured value of the real part of the chomo-magnetic coupling $\mathrm{Re}(\hat{\mu}_t)$ is found to be $-0.013 \pm 0.032$ with a corresponding 95% confidence interval of $-0.050< \mathrm{Re}(\hat{\mu}_t) < 0.076$.
Links: CDS record (PDF) ; inSPIRE record ; Public twiki page ; CADI line (restricted) ; These preliminary results are superseded in this paper, PRD 93 (2016) 052007. The superseded preliminary plots can be found here.

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