Search for CP violating top quark couplings in pp collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper reports a search for CP violation in top quark pair production at 13 TeV using CMS data, employing Lorentz scalar observables to measure asymmetries sensitive to the top quark's chromoelectric dipole moment, finding results consistent with the standard model.

Contribution

The study introduces a novel approach using Lorentz scalar observables to probe CP violation in top quark pairs at the LHC, providing new constraints on the top quark's chromoelectric dipole moment.

Findings

No evidence of CP violation was observed.

Results are consistent with standard model predictions.

Constraints on the top quark's chromoelectric dipole moment were improved.

Abstract

Results are presented from a search for CP violation in top quark pair production, using proton-proton collisions at a center-of-mass energy of 13 TeV. The data used for this analysis consist of final states with two charged leptons collected by the CMS experiment, and correspond to an integrated luminosity of 35.9 fb$^{-1}$. The search uses two observables, $\mathcal{O}_1$ and $\mathcal{O}_3$, which are Lorentz scalars. The observable $\mathcal{O}_1$ is constructed from the four-momenta of the charged leptons and the reconstructed top quarks, while $\mathcal{O}_3$ consists of the four-momenta of the charged leptons and the b quarks originating from the top quarks. Asymmetries in these observables are sensitive to CP violation, and their measurement is used to determine the chromoelectric dipole moment of the top quark. The results are consistent with the expectation from the standard model.