Comment on ``Neutrino masses and mixing angles in a predictive theory of fermion masses''

Abstract

In the extension of the Dimopoulos--Hall--Raby model of the fermion mass matrices to the neutrino sector, there is an entry in the up-quark and neutrino Dirac mass matrices which can be assumed to arise from the Yukawa coupling of a {\bf 120}, instead of a {\bf 10} or a {\bf 126}, of SO(10). Although this assumption leads to an extra undetermined complex parameter in the model, the resulting lepton mixing matrix exhibits the remarkable feature that the $ ν_τ $ does not mix with the other two neutrinos. Making a reasonable assumption about the extra parameter, we are able to fit the large-mixing-angle MSW solution of the solar-neutrino problem, and we obtain $ m_{ν_τ} \sim 10 $ eV, the right mass range to close the Universe. Other possibilities for explaining the solar-neutrino deficit are also discussed.