Natural flavour conservation and soft CP violation in grand unified theories: A phenomenological SO(10) model with a low intermediate mass scale

It is shown that the embedding in SO(10) of a recent approach ensuring natural flavor conservation and spontaneous CP violation in left-right-symmetric models is able to lead, with the minimal Higgs content and reasonable assumptions about Higgs-boson masses, to a low intermediate mass scale satisfying 0.234≤( sin^2 θ_W ) ≤0.226. In the scheme, the lower limit to the proton lifetime is rather near to the present experimental sensitivity and n↔ anti n oscillations are allowed with τ_n↔anti n=10^6-10^9 sec.