Measurement of the $t\bar{t}$ spin correlations and top quark polarization in dileptonic channel with the CMS detector

TL;DR

This paper reports on CMS measurements of top quark polarization and spin correlations in dileptonic $t\bar{t}$ events at 8 TeV, testing the Standard Model and constraining new physics scenarios.

Contribution

It provides the first detailed measurement of $t\bar{t}$ spin correlations and polarization in the dileptonic channel at 8 TeV with CMS data.

Findings

Results are consistent with Standard Model predictions.

Constraints are placed on supersymmetric top partner models.

The measurements improve understanding of top quark production dynamics.

Abstract

The degree of top polarization and strength of $t\bar{t}$ correlation are dependent on production dynamics, decay mechanism, and choice of the observables. At the LHC, measurement of the top polarization and spin correlations in $t\bar{t}$ production is possible through various observables related to the angular distribution of decay leptons. A measurement of differential distribution provides a precision test of the standard model of particle physics and probes for deviations, which could be a sign of new physics. In particular, the phase space for the super-symmetric partner of the top quark can be constrained. Results from the Compact Muon Solenoid (CMS) collaboration for top quark polarization and spin correlation in the dileptonic channel are reviewed briefly in this proceeding. The measurements are obtained using 19.5 fb$^{-1}$ of data collected in pp collisions at the center-of-mass energy of 8 TeV.