A two-generational SU(7) model with extended weak sector: mass hierarchies, mixings, and the flavor non-universality

Abstract

Abstract We study a possible gauge symmetry breaking pattern in an SU(7) grand unified theory, which describes the mass origins of all electrically charged SM fermions of the second and the third generations. Two intermediate gauge symmetries of G 341 ≡ SU 3 c ⊗ SU 4 W ⊗ U 1 X 0 $$ {\mathcal{G}}_{341}\equiv \textrm{SU}{(3)}_c\otimes \textrm{SU}{(4)}_W\otimes \textrm{U}{(1)}_{X_0} $$ and G 331 ≡ SU 3 c ⊗ SU 4 W ⊗ U 1 X 1 $$ {\mathcal{G}}_{331}\equiv \textrm{SU}{(3)}_c\otimes \textrm{SU}{(4)}_W\otimes \textrm{U}{(1)}_{X_1} $$ arise above the electroweak scale. SM fermion mass hierarchies between two generations can be obtained through a generalized seesaw mechanism. The mechanism can be achieved with suppressed symmetry breaking VEVs from multiple Higgs fields that are necessary to avoid tadpole terms in the Higgs potential. Some general features of the SU(7) fermion spectrum will be described, which include the existence of vectorlike fermions, the tree-level flavor changing weak currents between the SM fermions and heavy partner fermions, and the flavor non-universality between different SM generations from the extended weak sector.

Keywords

• Grand Unification
• New Gauge Interactions
• Theories of Flavour