SO(10) theory of R-parity and neutrino mass

We study the Higgs sector of a SO(10) grand unified theory which predicts exact conservation of R-parity at all scales and incorporates the see-saw mechanism. We find possible intermediate scales and light states compatible with the constraints coming from the running of the gauge couplings. Such a pattern could lower the SO(10) breaking scale, allowing the d = 6 proton decay operators to be comparable in magnitude to the d = 5 ones. (C) 2001 Elsevier Science B.V. All rights reserved.