Mass Relations, Unification, and Proton Decay in the Mirror GUT Model

Abstract

We propose an SU(5)$\times $U(1)$_\text{X}\times$U(1)$_\text{PQ}$ model without SUSY because the SUSY particles have not been observed yet. The $\mathrm{U(1)_{X}}$ gauge symmetry is the generalization of the $\mathrm{U(1)_{B-L}}$ gauge symmetry and $\mathrm{U(1)_{PQ}}$ symmetry is the global Peccei-Quinn symmetry. We introduce three mirror families in order to unify the SM gauge couplings and avoid the restriction of proton lifetime. In order to obtain the difference of the masses for the down-type quarks and charged leptons, we also introduce the $\mathbf{45}$ representation Higgs in addition to the $\mathbf{5}$ representation one. In this paper, we discuss the mass relations between the SM and mirror particles and identify the mass scales of the mirror particles. Since the new particles exist in the intermediate energy scale and contribute to the renormalization group equation, the SM gauge couplings unify successfully at high energy. Our model can be tested by the future proton decay search, e.g., the Hyper-Kamiokande experiment expected as $\tau_p(p\to\pi^0{e^+})<1.0\times10^{35}$ years. Also, by using the mass relations between the active and mirror neutrinos, we estimate the lower bound of the heavy neutrino masses.