Bounds on the absorptive parts of the chromomagnetic and chromoelectric dipole moments of the top quark from LHC data

TL;DR

This paper derives bounds on the imaginary parts of the top quark's chromomagnetic and chromoelectric dipole moments using recent LHC data, providing constraints relevant for new physics models.

Contribution

It reinterprets LHC data to set limits on the absorptive parts of top quark dipole moments, a novel approach to constraining CP-violating effects.

Findings

Limits on the imaginary parts are of order 10^{-1} to 10^{-2}

No significant deviation from the standard model observed

Bounds are useful for constraining new physics models

Abstract

Bounds on the absorptive (imaginary) parts of the top quark chromomagnetic $\hat{\mu}_t$ and chromoelectric $\hat{d}_t$ dipole moments are obtained by reinterpreting the most recent LHC data in top quark pair production. It is found that both limits are of the order of $10^{-1}-10^{-2}$, which are consistent with the standard model prediction of ${\rm Im}\big[\hat{\mu}_t\big]$. The effects of the absorptive parts of the top quark dipole moments are also studied via some kinematic distributions of $\bar{t}t$ production, though no significant deviation from the standard model leading order contribution is observed. Our bounds can be useful to constrain the parameter space of standard model extensions.