  A search for invisible decays of Higgs bosons is performed using the vector
boson fusion and associated ZH production modes. In the ZH mode, the Z boson is
required to decay to a pair of charged leptons or a b b-bar quark pair. The
searches use the 8 TeV pp collision dataset collected by the CMS detector at
the LHC, corresponding to an integrated luminosity of up to 19.7 inverse
femtobarns. Certain channels include data from 7 TeV collisions corresponding
to an integrated luminosity of 4.9 inverse femtobarns. The searches are
sensitive to non-standard-model invisible decays of the recently observed Higgs
boson, as well as additional Higgs bosons with similar production modes and
large invisible branching fractions. In all channels, the observed data are
consistent with the expected standard model backgrounds. Limits are set on the
production cross section times invisible branching fraction, as a function of
the Higgs boson mass, for the vector boson fusion and ZH production modes. By
combining all channels, and assuming standard model Higgs boson cross sections
and acceptances, the observed (expected) upper limit on the invisible branching
fraction at m[H] = 125 GeV is found to be 0.58 (0.44) at 95% confidence level.
We interpret this limit in terms of a Higgs-portal model of dark matter
interactions.
