Search for dark matter in Z+MET events with the CMS detector

The origin of Dark Matter is one of the most important and challenging questions in high energy physics today. To date, Dark Matter has only been observed indirectly via its gravitational impact on the kinematics of galaxies. However, it is expected that Dark Matter can also be indirectly observed in collider experiments, such as CMS at the Large Hadron Collider. A search for hints of Dark Matter is performed in the data collected by CMS in 2012. The Dark Matter particles recoil against a leptonically decaying Z boson, leading to the distinct signature of two isolated leptons and missing transverse energy. Different aspects of the background determination and its systematic uncertainties are presented. The obtained results are used for setting limits on different parameters of an Effective Field Theory for several coupling scenarios. The results are also interpreted in an Unparticle model.