IsSU(2)L×SU(2)R×UB−L(1)a viable symmetry at low energy?

We consider the gauge groups $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L\times \mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_R\times {\mathrm{U}}_{B-L}\mathrm{}\left(1\right)\mathrm{}$ with low-energy parity restoration and $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L\times T_{3R}\times {\mathrm{U}}_{B-L}\mathrm{}\left(1\right)\mathrm{}$ as alternatives to the standard model at low energies, and fit their parameters to the neutral-current data. It is shown that if present phenomenological fits to data are taken seriously, the left-right-symmetric model is disfavored because it requires either too small a value of ${{sin}^2\theta }_W$ to be consistent with grand unification or if ${{sin}^2\theta }_W$ is chosen at a reasonable value, it then requires an imaginary mass for one of the $Z$ bosons. The second gauge group is consistent with data, and the best fits yield ${{sin}^2\theta }_W\simeq 0.24$ and $M_{Z_1}=88\mathrm{}\pm 8$ GeV, $M_{Z_2}\sim 230$ GeV.