Suppression of scalar mediated FCNCs in a SU(3)_c× SU(3)_L× U(1)_X -model

The models based on SU(3)C × SU(3)L × U(1)X gauge symmetry (331-models) have been advocated to explain the number of fermion families. These models place one quark family to a different representation than the other two. The traditional 331-models are plagued by scalar mediated quark flavour changing neutral currents (FCNC) at tree- level. So far there has been no concrete mechanisms to suppress these FCNCs in 331- models. Recently it has been shown that the Froggatt-Nielsen mechanism can be incorporated into the 331-setting in an economical fashion (FN331-model). The FN331-model explains both the number of fermion families in nature and their mass hierarchy simultaneously. In this work we study the Higgs mediated quark FCNCs in FN331-model. The flavour violating couplings of quarks are suppressed by the ratio of the SU(2)L × U(1)Y and SU(3)L × U(1)X breaking scales. We find that the SU(3)L × U(1)X -breaking scale can be as low as 5 TeV in order to pass the flavour bounds.