Bottom-tau unification by neutrinos in a nonsupersymmetric SU(5) model

T Tsuyuki

doi:10.1093/ptep/ptu175

Abstract

We show that Yukawa couplings of bottom quarks and tau leptons can be unified in a non-supersymmetric SU(5) model. We introduce an arbitrary number of right-handed neutrinos. Their masses and Yukawa couplings that satisfy the unification condition by renormalization group evolution are shown. In the case that the grand unification scale is $10^{15.5}$GeV and three right-handed neutrinos have the same mass, the upper bound on their mass is $\sim 10^{14.1}$GeV.

Highlights

Neutrino oscillations, which mean that neutrinos have masses, are evidence for physics beyond the Standard Model (SM)
The simplest grand unification theory (GUT) is the model based on the SU(5) gauge group [9], which is broken down to GSM in one step
By solving renormalization group equations (RGEs) (3) to (6) and using the initial condition (11), we found that yb and yτ are unified within the experimental errors

Summary

Introduction

Neutrino oscillations, which mean that neutrinos have masses, are evidence for physics beyond the Standard Model (SM). The neutrino masses can be induced by singlet, right-handed neutrinos (type-I [1,2,3]), an SU(2) triplet scalar (type-II [4,5,6]) or SU(2) triplet fermions (type-III seesaw [7]). By solving renormalization group equations (RGEs), the three gauge couplings evolve toward unification, but do not exactly meet at one scale. If some fields charged under GSM exist between the electroweak scale and the GUT scale (MG), unification is still possible.

Results

Conclusion