  A search for dark matter and unparticle production at the LHC has been
performed using events containing two charged leptons (electrons or muons),
consistent with the decay of a Z boson, and large missing transverse momentum.
This study is based on data collected with the CMS detector in 2015,
corresponding to an integrated luminosity of 2.3 inverse femtobarns of
proton-proton collisions at the LHC, at a center-of-mass energy of 13 TeV. No
excess over the standard model expectation is observed. Compared to previous
searches in this topology, which exclusively relied on effective field
theories, the results are interpreted in terms of a simplified model of dark
matter production for both vector and axial vector couplings between a mediator
and dark matter particles. The first study of this class of models using CMS
data at sqrt(s) = 13 TeV is presented. Additionally, effective field theories
of dark matter and unparticle production are used to interpret the data.
