Bottom-tau unification by neutrinos in a nonsupersymmetric SU(5) model
  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. 
Takanao Tsuyuki
hep-ph