Large Majorana Mass from the Anomalous U(1) Gauge Symmetry
  We show a new and simple model which induces large Majorana masses of right-handed neutrinos. It is based on U(1)_X anomalous gauge symmetry, which is cancelled by the Green-Schwarz mechanism. These Majorana masses can solve the solar neutrino problem by the vacuum oscillation mechanism. The superpotential of this model is scale invariant. The field contents are simple extensions of the MSSM, which have four standard gauge singlet fields, two extra vector-like fields, and right-handed neutrinos in addition to the MSSM. 
Naoyuki Haba