  We consider a generic framework where the Standard Model (SM) coexists with a
hidden sector endowed with some additional gauge symmetry. When this symmetry
is broken by a scalar field charged under the hidden gauge group, the
corresponding scalar boson generally mixes with the SM Higgs boson. In
addition, massive hidden gauge bosons emerge and via the mixing, the observed
Higgs-like mass eigenstate is the only known particle that couples to these
hidden gauge bosons directly.
  We study the LHC monojet signatures of this scenario and the corresponding
constraints on the gauge coupling of the hidden gauge group as well as the
mixing of the Higgs scalars.
