Constraining the dipole moments of the top quark

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 2 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 $t\overline{t}$ spectrum by the ATLAS collaboration. We also update the indirect constraints on electric and magnetic dipole moments from radiative $b\ensuremath{\rightarrow}s$ transitions, finding that they can be considerably larger than their colored counterparts.