Flavor violation in chromo- and electromagnetic dipole moments induced by $Z^\prime$ gauge bosons and a brief revisit of the Standard Model

TL;DR

This paper estimates flavor-changing neutral current-induced dipole moments of the tau lepton and top quark mediated by a new $Z'$ gauge boson in models beyond the Standard Model, providing analytic expressions and comparing with Standard Model predictions.

Contribution

It introduces analytic formulas for dipole moments induced by $Z'$ gauge bosons in BSM models and revisits Standard Model predictions, including imaginary parts.

Findings

Tau magnetic dipole moment ~10^{-8}

Tau electric dipole moment ~10^{-24} e cm

Top chromomagnetic dipole moment ~10^{-6}

Abstract

The electromagnetic dipole moments of the tau lepton and the chromoelectromagnetic dipole moments of the top quark are estimated via flavor-changing neutral currents, mediated by a new neutral massive gauge boson. We predict them in the context of models beyond the Standard Model with extended current sectors, in which simple analytic expressions for the dipole moments are presented. For the different $Z^\prime$ gauge boson considered, the best prediction for the magnetic dipole moment of the tau lepton, $|a_\tau|$, is of the order of $10^{-8}$, while the highest value for the electric one, $|d_\tau|$, corresponds to $10^{-24}$ $e\,$cm; our main result for the chromomagnetic dipole moment of the top quark, $|\hat{\mu}_t|$, is $10^{-6}$, and the value for the chromoelectric one, $|d_t|$, can be as high as $10^{-22}$ $e\,$cm. We compare our results, revisiting the corresponding Standard Model predictions, in which the chromomagnetic dipole moment of the top quark is carefully evaluated, finding explicit imaginary contributions.