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In the present work the Z ′ tc coupling is bounded by using the current experimental data on the D 0 − D 0 meson mixing system. It is found that the strength associated to this coupling is less than 5.75 × 10 −2 . The single top production through the e + e − → Z ′ → tc process at the Z ′ boson resonance is studied and we found that around 10 7 tc events will be expected at the International Linear Collider. For the Z ′ → tc decay, we predict a branching ratio of 10 −2 .

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 0 gauge boson considered, the best prediction for the magnetic dipole moment of the tau lepton, ja τ j, is of the order of 10 −8 , while the highest value for the electric one, jd τ j, corresponds to 10 −24 e cm; our main result for the chromomagnetic dipole moment of the top quark, jμ t j, is 10 −6 , and the value for the chromoelectric one, jd t j, 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.

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