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

There are several indications that the Majorana masses of the right-handed neutrino components, MR, are at the intermediate scale: MR∼(1010−1012) GeV or even lighter. The renormalization effects due to large Yukawa couplings of neutrinos from region of momenta MR⪅q⪅MG are studied in the supersymmetric standard model. It is shown that neutrino renormalization effect can increase the mb/mτ ratio up to (10–15) %. This strongly disfavours mb−mτ unification for low values of tanβ<10 especially at large values of αs. Lower bounds on MR and tanβ 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.