  A search for evidence of particle dark matter (DM) and unparticle production
at the LHC has been performed using events containing two charged leptons,
consistent with the decay of a Z boson, and large missing transverse momentum.
This study is based on data collected with the CMS detector corresponding to an
integrated luminosity of 19.7 inverse femtobarns of pp collisions at the LHC at
a center-of-mass energy of 8 TeV. No significant excess of events is observed
above the number expected from the standard model contributions. The results
are interpreted in terms of 90% confidence level limits on the DM-nucleon
scattering cross section, as a function of the DM particle mass, for both
spin-dependent and spin-independent scenarios. Limits are set on the effective
cutoff scale Lambda, and on the annihilation rate for DM particles, assuming
that their branching fraction to quarks is 100%. Additionally, the most
stringent 95% confidence level limits to date on the unparticle model
parameters are obtained.
