Flavor-changing neutral currents in the minimal 3-3-1 model revisited

We study a fewF ¼ 2 andF ¼ 1 flavor-changing neutral current processes in the minimal 3-3-1 model by considering, besides the neutral vector bosons Z 0 , the effects due to one CP-even and one CP-odd scalar. We find that there are processes in which the interference among all the neutral bosons is constructive or destructive and in others the interference is negligible. We first obtain numerical values for all the unitary matrices that rotate the left- and right-handed quarks and give the correct mass of all the quarks in each charge sector and the Cabibbo-Kobayashi-Maskawa (CKM) mixing matrix. The so-called 3-3-1 models with gauge symmetry SUð3ÞCSUð3ÞLUð1ÞX are interesting extensions of the standard model (SM). The main feature of these models is that, by choosing appropriately the representation con- tent, the triangle anomalies cancel out, and the number of families has to be a multiple of three. Moreover, because of the asymptotic freedom, this number is just three (1-3). In particular, the minimal version of this class of models (m3- 3-1 for short) (1) has other interesting predictions: It ex- plains why sin 2 � W < 1=4 is observed, and at the same time, when sin 2 � W ¼ 1=4, it implies the existence of a Landau-like pole at energies of the order of a few TeVs (4). The existence of this Landau-like pole also stabilizes the electroweak scale avoiding the hierarchy problem (5), and the model allows the quantization of electric charge inde- pendently of the nature of the massive neutrinos (6,7). It also has an almost automatic Peccei-Quinn symmetry if the trilinear term in the scalar potential becomes a dynamical degree of freedom (8), there are also new sources of CP violations which allow to obtainand � 0 =� even without the Cabibbo-Kobayashi-Maskawa (CKM) phase; i.e., if we put � ¼ 0 (9). And, probably, it could explain CPviolation in the B � B mesons as well. One important feature that distinguishes the model from any other one is the predic- tion of extra singly charged and doubly charged gauge boson bileptons (10) and also exotic charged quarks, while the lepton sector is the same as that of the SM. Right- handed neutrinos are optional in the model. They are not needed to generate light active neutrinos or the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing ma- trix. Those exotic charged particles may have an effect on the two photon decay of the SM-like Higgs scalar (11). A common feature of all 3-3-1 models is that two of the quark triplets transform differently from the third one, and this implies flavor-changing neutral currents (FCNC) at tree level mediated by the extra neutral vector boson, Z 0