On the problem of quark-lepton families

TL;DR

This paper explores the possibility of unifying quark and lepton families through a horizontal gauge symmetry, suggesting new fermion generations could explain dark matter or influence flavor mixing.

Contribution

It proposes a horizontal $SU(3)_H$ symmetry framework for family unification, allowing for new quark and lepton generations with potential dark matter implications.

Findings

Horizontal symmetry can unify three known families.

New fermion generations could be stable or unstable.

Stable generations may serve as dark matter candidates.

Abstract

The problem of quark-lepton families is discussed in the "bottom-up" phenomenological approach to the extensions of the Standard model. It provides the possibility of the {\it Horizontal unification} of the three known families on the basis of horizontal gauge flavor $SU(3)_H$ symmetry. The new generations of quarks and leptons can exist. If unstable and mixed with light fermions, they should contribute the CKM matrix. If stable and decoupled from known families, new generations can provide new candidates for dark matter.