  This article reports on a search for dark matter pair production in
association with a Higgs boson decaying to a pair of bottom quarks, using data
from $20.3 fb^{-1}$ of $pp$ collisions at a center-of-mass energy of 8 TeV
collected by the ATLAS detector at the LHC. The decay of the Higgs boson is
reconstructed as a high-momentum $b\bar{b}$ system with either a pair of
small-radius jets, or a single large-radius jet with substructure. The observed
data are found to be consistent with the expected Standard Model backgrounds.
Model-independent upper limits are placed on the visible cross-sections for
events with a Higgs boson decaying into $b\bar{b}$ and large missing transverse
momentum with thresholds ranging from 150 GeV to 400 GeV. Results are
interpreted using a simplified model with a $Z^\prime$ gauge boson decaying
into different Higgs bosons predicted in a two-Higgs-doublet model, of which
the heavy pseudoscalar Higgs decays into a pair of dark matter particles.
Exclusion limits are also presented for the mass scales of various effective
field theory operators that describe the interaction between dark matter
particles and the Higgs boson.
