Abstract: While the gravitational evidence for the existence of Dark Matter (DM) is overwhelming, there is no good DM candidate among the particles of the Standard Model, and there is no evidence yet for non-gravitational interactions between DM and Standard Model particles. A search is described for evidence of particle DM production with a signature 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 fb-1 of proton-proton collisions at the LHC at a center-of-mass energy of 8 TeV. The results are interpreted in terms of limits on the DM-nucleon scattering cross section, as a function of the DM particle mass, for both spin-dependent and spin-independent scenarios.

A related study searches for invisible decays of Higgs bosons in associated ZH production, using the same final state with a Z boson and missing transverse mometum. The study uses the full 2011 and 2012 data samples at 7 TeV and 8 TeV, respectively. The search is 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. By assuming Standard Model Higgs boson cross sections and acceptances, an upper limit is obtained on the invisible branching fraction of the Higgs boson. The limit is also interpreted in terms of a Higgs-portal model of DM interactions.