Neutrinos and structure of the intermediate mass scale

Abstract

Neutrino data lead via the see-saw mechanism to masses of the right handed\nneutrinos at the intermediate mass scale. Simple formalism is suggested which\nincorporates the quark - lepton symmetry and allows one to find properties of\nthe intermediate scale (masses and mixing) from neutrino data. Averaged mass\nscale and the mass hierarchy parameter are introduced and fixed by the data.\nThey determine natural ranges of masses and mixing at the intermediate scale.\nIn particular, scenario which includes the MSW solution of the solar neutrino\nproblem and tau neutrino as the hot component of Dark Matter of the Universe\nleads to $M_2 = (2 - 4) \\cdot 10^{10}$ GeV and $M_3 = (4 - 8) \\cdot 10^{12}$\nGeV in agreement with the linear mass hierarchy. Strong deviations from the\nnatural ranges imply fine tuning of parameters or/and certain symmetry of the\nMajorana mass matrix of the right handed neutrinos.\n