Neutrino masses and b−τ unification in the supersymmetric standard model

Abstract There are several indications that the Majorana masses of the right-handed neutrino components, M R , are at the intermediate scale: M R ∼(10 10 −10 12 ) GeV or even lighter. The renormalization effects due to large Yukawa couplings of neutrinos from region of momenta M R ⪅ q ⪅ M G are studied in the supersymmetric standard model. It is shown that neutrino renormalization effect can increase the m b / m τ ratio up to (10–15) %. This strongly disfavours m b − m τ unification for low values of tan β α s . Lower bounds on M R and tan β from the b − τ unification condition were found. The implications of the results to the see-saw mechanism of the neutrino mass generation are discussed.