TeV scale horizontal gauge symmetry and its implications in B-physics

Understand

We propose a gauged $U(1)_{H}$ horizontal symmetry around TeV scale that is a subgroup of a $SU(3)_{H}$ horizontal gauge symmetry broken at ${\cal O}(10^{14}) \GeV$.

• The breaking generates right-handed Majorana neutrino masses through a $SU(3)_H$ sextet scalar.
• A particular Majorana right-handed neutrino mass matrix explicitly determines the remnant $U(1)_{H}$ at low energy which only couples to $b-s$ and $\mu-\tau$ in the gauge eigenstate.
• The dangerous $K-\bar{K}$, $D-\bar{D}$ mixing and $B_s \rightarrow \mu^+ \mu^-$ are kept to be safe because the relevant couplings are suppressed through high powers of small mixing angles in the fermion rotation matrix.