Study of ZZ to four leptons events in ATLAS at the LHC and upgrade of the ATLAS Muon Spectrometer

The study of the ZZ and ZZ* production in proton-proton collisions at the Large Hadron Collider (LHC) at CERN is presented. The data analyzed in this study were recorded by the ATLAS experiment at a centre-of-mass energy of 7 TeV and of 8 TeV. The selected events are consistent with fully leptonic ZZ decays, in particular to electrons and muons. The total ZZ production cross section is measured and is found to be in agreement with the Standard Model (SM) prediction. The ZZ production allows the study of the anomalous neutral Triple Gauge Couplings. No deviation from the SM prediction is found that could indicate the presence of New Physics. In view of the forthcoming increase of the instantaneous luminosity of the LHC, the ATLAS Collaboration foresees upgrades of the detector. An upgrade of the Muon Spectrometer is presented. The integration of the new detection elements in the ATLAS Geometry is illustrated, as well as the increase in the total Barrel acceptance.