  A light vector boson, Z_d, associated with a "dark sector" U(1)_d gauge group
has been introduced to explain certain astrophysical observations as well as
low energy laboratory anomalies. In such models, the Higgs boson may decay into
X+Z_d, where X=Z, Z_d or \gamma. Here, we provide estimates of those decay
rates as functions of the Z_d coupling through either mass-mixing (e.g. via an
enlarged Higgs mechanism) or through heavy new fermion loops and examine the
implied LHC phenomenology. Our studies focus on the higher m_{Z_d} case, >
several GeV, where the rates are potentially measurable at the LHC, for
interesting regions of parameter spaces, at a level complementary to low energy
experimental searches for the Z_d. We also show how measurement of the Z_d
polarization (longitudinal versus transverse) can be used to distinguish the
physics underlying these rare decays.
