Neutrino masses and electron-muon-τ-lepton universality

By a simple extension of the standard electroweak gauge group to SU_L(2)×U_e(1)×U_μ(1)×U_τ(1), it is shown that it is possible to get light-neutrino masses in the range of a few electron volts. For this purpose it is necessary that M_R, the mass scale associated with the masses of superheavy neutrinos which carries U_i(1) quantum numbers and which is related to the scale at which e-μ-τ universality is broken, is to be greater than 10⁹ GeV. However, for the solar-neutrino problem M_R should be in the range of 10¹¹-10¹² GeV. In particular, we obtain two Majorana neutrinos of almost equal mass and one Majorana neutrino (predominantly an electron neutrino) of almost zero mass.