Grand unification and parity restoration at low energies. II. Unification constraints

In this second paper in the series, we show how the embedding of $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L\times \mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_R\times \mathrm{U}{\mathrm{}\left(1\right)\mathrm{}}_{B-L}$ in SO(10) grand unified theory suggests the possibility of parity being restored at low energies, thus providing an alternative to conventional theories with a desert above $M_W$. Some important predictions of the model are stressed: appreciable Majorana neutrino masses, lepton-number violation in neutrinoless double-$\beta$ decay with $\eta \simeq {10}^{-4\mathrm{}}-{10}^{-5\mathrm{}}$, and the absence of observable proton decay (${\tau }_p\simeq {10}^{38}-{10}^{46}$ years). From the phenomenological analysis in our earlier work and the unification constraints presented here we find that, if the above picture is correct, $150\le {M_W}_R\le 240$ GeV. We argue that both the charged and neutral gauge bosons of the second generation should be produced at ISA-BELLE energies with significant rates.