Constraining the dipole moments of the top quark

TL;DR

This paper refines bounds on top quark dipole moments using experimental data, showing that certain CP-violating effects are highly constrained, impacting future searches for new physics at colliders.

Contribution

It provides the most stringent bounds to date on top quark dipole moments, especially the chromo-electric dipole moment, and discusses implications for new physics models.

Findings

Neutron EDM limits strongly constrain top chromo-electric dipole moment.

Bounds on CP-violating dipole moments are improved by two orders of magnitude.

Constraints on electric and magnetic dipole moments from B decays can be larger than colored counterparts.

Abstract

We investigate the direct and indirect bounds on dipole operators involving the top quark. A careful analysis shows that the experimental upper limit on the neutron electric dipole moment strongly constrains the chromo-electric dipole of the top. We improve previous bounds by two orders of magnitude. This has significant implications for new physics models and it also means that CP violation in top pair production mediated by dipole operators will not be accessible at the LHC. The CP conserving chromo-magnetic dipole moments are constrained by recent measurements of the t\bar t spectrum by the ATLAS collaboration. We also update the indirect constraints on electric and magnetic dipole moments from radiative b -> s transitions, finding that they can be considerably larger than their colored counterparts.