Observation of single resonance Z$\to $4l in pp collisions with the ATLAS detector

This talk will present the observation of single resonance Z boson decays to four leptons in proton-proton collisions data collected by the ATLAS detector. The single resonance peak from Z$\to $4l provides a natural standard candle for the Higgs boson search in the H$\to $ZZ*$\to $4l channel. The cross section and the branching ratio of the single resonance Z$\to $4l production measured using 7 TeV and 8 TeV data will be reported.