Simulation, selection and reconstruction of dark Z bosons decaying into collimated leptons in proton-proton collisions at √8=13 TeV with the ATLAS detector.

The existence of dark Z bosons has been predicted by several models and such dark Z bosons can decay into lepton jets and have long life time such that displaced decay can happen inside or even outside of the ATLAS detector. In this project, several simulations were done for different processes and different couplings between dark Z boson and the hypercharge gauge boson. Selections and reconstructions were done and further analysis are still yet to be done.