Study of Mono-Z Production at the LHC as Evidence of Dark Matter
The existence of Dark Matter (DM) has been inferred from its cosmological signals, what allows its search in particle accelerators experiments. Exploring physics beyond the Standard Model is one of the main objectives of the CMS experiment at CERN LHC. Given that DM particles should not interact with the detectors, such particles can be searched for in the form of missing transverse energy (MET), the so called mono-X searches. A simplified model is used to approach this kind of new physics, considering DM as a Dirac fermion and a new mediator between DM and SM particles as a neutral scalar boson. Due to the high mass of the mediator, if a Z boson recoils against it, the products of its decay will have large momentum and be collimated. The main backgrounds for a mono-Z search are ZZ, WZ and WW production, with a dilepton signature and some missing energy. This study will show possible kinematical cuts for the signal improvement over expected backgrounds. This work uses standart tools, such as MadGraph and Pythia for the generation, and the CMSSW framework to perform CMS detector simulation and data reconstruction. The reconstructed simulated data is then transformed into the more compact NanoAOD format and analysed with ROOT, using the standalone NanoAOD-Tools package.