How Can We Obtain a Large Majorana-Mass in Calabi-Yau Models ?

Abstract

In a certain type of Calabi-Yau superstring models it is clarified that the symmetry breaking occurs by stages at two large intermediate energy scales and that two large intermediate scales induce large Majorana-masses of right-handed neutrinos. Peculiar structure of the effective nonrenormalizable interactions is crucial in the models. In this scheme Majorana-masses possibly amount to $O(10^{9\sim 10}\text{gev})$ and see-saw mechanism is at work for neutrinos. Based on this scheme we propose a viable model which explains the smallness of masses for three kind of neutrinos ${\nu }_e,{\nu }_{\mu }\mathrm{and}{\nu }_{\tau }$. Special forms of the nonrenormalizable interactions can be understood as a consequence of an appropriate discrete symmetry of the compactified manifold.

Comments: 30-pages + 6-figures, LaTeX, Preprint DPNU-94-02, AUE-01-94