NEUTRINO MASSES WITHIN THE MINIMAL SUPERSYMMETRIC STANDARD MODEL

We investigate the possibility of accommodating neutrino masses compatible with the Mikheyev-Smirnov-Wolfenstein study of the solar neutrino deficit within the minimal supersymmetric standard model. The "gravity-induced" seesaw mechanism based on an interplay of nonrenormalizable and renormalizable terms in the superpotential allows neutrino masses m(nu) is-proportional-to m(u)2/M(I), with m(u) the corresponding quark mass and M(I) congruent-to 4 X 10(11) GeV, while at the same time ensuring the grand desert with the gauge coupling unification at M(U) congruent-to 2 X 10(16) GeV. The proposed scenario may be realized in a class of string vacua, i.e., large radius (R2/alpha' approximately 20) (0,2) Calabi-Yau spaces. In this case M(U)2 = M(C)2/O(2R2/alpha') and M(I)=O(e(-R2/alpha'))M(C). Here M(C)=g X 5.2 X 10(17) GeV is the scale of the tree-level (genus-zero) gauge coupling (g) unification.