Chromomagnetic and chromoelectric dipole moments of quarks in the reduced 331 model

Abstract: The one-loop contributions to the chromomagnetic dipole moment $\hat\mu_t(q<sup>2)$ and electric dipole moment $\hat d_t(q<sup>2)$ of the top quark are calculated within the reduced 331 model (RM331) in the general case of an off-shell gluon. It is argued that the results are gauge independent for $q^2\ne 0$ and represent valid observable quantities. In the RM331 $\hat \mu_t(q<sup>2)$ receives new contributions from two heavy gauge bosons $Z&#39;$ and $V<sup>+$ and a new neutral scalar boson $h_2$, along with a new contribution from the standard model Higgs boson via flavor changing neutral currents. The latter, which are also mediated by the $Z&#39;$ gauge boson and the scalar boson $h_2$, can give a non-vanishing $\hat d_t$ provided that there is a $CP$-violating phase. The analytical results are presented in terms of both Feynman parameter integrals and Passarino-Veltman scalar functions, which are useful to cross-check the numerical results. Both $\hat\mu_t(q<sup>2)$ and $\hat d_t$ are numerically evaluated for parameter values still allowed by the constraints from experimental data. It is found that the new one-loop contributions of the RM331 to $\hat \mu_t(q<sup>2)$ are of the same order of magnitude or larger than in other standard model extensions, with the dominant contribution arising from the $V<sup>+$ gauge boson for $|q|$ in the 30-1000 GeV interval and a mass $m_{V}$ of the order of a few hundreds of GeVs. As for $\hat d_t(q<sup>2)$, it receives the largest contribution from $h_2$ exchange and can reach values of the order of $10<sup>{-20}$, which is smaller than the contributions predicted by other standard model extensions.