  A weighted average weak mixing angle theta_W derived from relatively low Q^2
experiments is compared with the Standard Model prediction obtained from
precision measurements. The approximate 1.8 sigma discrepancy is fit with an
intermediate mass (~ 10-35 GeV) "dark" Z boson Z_d, corresponding to a U(1)_d
gauge symmetry of hidden dark matter, which couples to our world via kinetic
and Z-Z_d mass mixing. Constraints on such a scenario are obtained from
precision electroweak bounds and searches for the rare Higgs decays H -> Z Z_d
-> 4 charged leptons at the LHC. The sensitivity of future anticipated low Q^2
measurements of sin^2 theta_W(Q^2) to intermediate mass Z_d is also
illustrated. This dark Z scenario can provide interesting concomitant signals
in low energy parity violating measurements and rare Higgs decays at the LHC,
over the next few years.
