Hierarchical fermions and detectable Z′ from effective two-Higgs-triplet 3-3-1 model

Abstract

We develop a SUð3Þ C ⊗ SUð3Þ L ⊗ Uð1Þ X model where the number of fermion generations is fixed by cancellation of gauge anomalies, being a type of 3-3-1 model with new charged leptons. Similarly to the economical 3-3-1 models, symmetry breaking is achieved effectively with two scalar triplets so that the spectrum of scalar particles at the TeV scale contains just two CP even scalars, one of which is the recently discovered Higgs boson, plus a charged scalar. Such a scalar sector is simpler than the one in the Two Higgs Doublet Model, hence more attractive for phenomenological studies, and has no flavor changing neutral currents (FCNC) mediated by scalars except for the ones induced by the mixing of Standard Model (SM) fermions with heavy fermions. We identify a global residual symmetry of the model which guarantees mass degeneracies and some massless fermions whose masses need to be generated by the introduction of effective operators. The fermion masses so generated require less fine-tuning for most of the SM fermions and FCNC are naturally suppressed by the small mixing between the third family of quarks and the rest. The effective setting is justified by an ultraviolet completion of the model from which the effective operators emerge naturally. A detailed particle mass spectrum is presented, and an analysis of the Z 0 production at the LHC run II is performed to show that it could be easily detected by considering the invariant mass and transverse momentum distributions in the dimuon channel.

Dynamical symmetry breaking and fermion mass hierarchy in the scale-invariant 3-3-1 model

“…As shown in Ref. [68], a residual symmetry associated with Uð1Þ PQ remains unbroken after spontaneous symmetry breaking. Such an unbroken symmetry is chiral with respect to the second components of the fermion (anti)triplets and their rh singlet counterparts, forbidding, in this way, the appearance of mass terms for these fields.…”

“…Note that the case where both neutral components of χ get vev is physically indistinguishable from the current one due to a reparametrization symmetry connecting the second and third components of the triplet; see Ref. [68] for more details. The tree-level scalar potential takes the following simple form:…”

“…Meanwhile, all the remaining scalar degrees of freedom are absorbed in the Higgs mechanism as shown in Ref. [68]. Therefore, the scalar spectrum is very compact.…”

“…It is worth pointing out that the issue of fermion mass hierarchy and mixing in 3-3-1 models has already been explored by some of us in Refs. [68,69]. Other interesting solutions to this issue have also been proposed by other authors with the use of discrete symmetries in Refs.…”

Vectorlike leptons and inert scalar triplet: Lepton flavor violation, g−2 , and collider searches

“…3-3-1 models are based on the SUð3Þ C × SUð3Þ L × Uð1Þ N gauge symmetry and were originally introduced since they offer a plausible answer to the number of generations in the Standard Model. These models have been extensively studied in contexts such as dark matter [44][45][46][47][48][49][50][51][52][53][54][55][56], flavor physics [57][58][59][60][61], neutrino masses [62][63][64][65][66][67][68][69][70][71], and collider physics [72][73][74][75].…”