Proton Stability in S_4 x Z_2 Flavor Symmetric Extra U(1) Model

TL;DR

This paper explores how an S_4 x Z_2 flavor symmetry in an E_6 inspired U(1) model can naturally suppress proton decay, linking proton stability to vacuum expectation values and exotic quark masses.

Contribution

It classifies suppression mechanisms of proton decay within a flavor symmetric E_6 inspired model and identifies conditions for proton stability related to VEVs and exotic quark masses.

Findings

Proton lifetime can be extended via flavor symmetry suppression mechanisms.

Allowed VEV regions exist for TeV-scale exotic quark masses.

Right-handed neutrino mass is constrained around 10^{12} GeV.

Abstract

We consider proton stability based on E_6 inspired extra U(1) model with S_4 x Z_2 flavor symmetry. In this model, a long life time of proton is realized by the flavor symmetry in several ways. We classify the suppression mechanisms of proton-decay and explain how the flavor symmetry works. There is an interesting solution, such as, in a special direction of vacuum expectation value (VEV), baryon number violating interactions are canceled. In the case that the suppression of proton decay is realized by the appropriate size of VEV, the allowed region of VEV exists when the exotic quark mass is O(TeV). From the constraint for the life time of exotic quark, the right handed neutrino mass should be in narrow range around 10^{12} GeV.