The simplest 3-3-1 model

Abstract

A simple extension of the Standard Model (SM), based on the gauge group [Formula: see text] with [Formula: see text] being the hypercharge, is considered. We show that, by imposing an approximate global [Formula: see text] custodial symmetry at the SM energy scale, the [Formula: see text] mixing is absent at tree level and the value of the [Formula: see text] parameter can be kept close to one. Tree-level flavor-changing neutral currents (FCNCs) are also reduced to three particles, namely [Formula: see text], a CP-odd Higgs and a CP-even Higgs. The model predicts new leptons with electric charges of ±1/2e and new quarks with ±1/6e charges as well as new gauge and scalar bosons with ±1/2e charges. Electric charge conservation requires that one of them must be stable. Their masses are unfortunately free parameters.