ATLAS Event Display: WZ polarization

Event display of a WZ → eν μμ candidate. The Z boson candidate decays into two muons (red lines). The W boson candidate decays into an electron, identified from its energy deposits in the cells of the electromagnetic calorimeter (green bars), and a neutrino (unobserved). The missing transverse momentum of the event has a value of 204 GeV, and is indicated by the dotted white line. On the left, a transverse projection shows the inner area of the detector, where also the tracks of charged particles (yellow) are visualised. On the right, a view of the detector showing, starting from the interaction point at the centre, the inner detector, the electromagnetic and hadronic calorimeters, and the muon chambers (blue and green boxes) associated with the two muon tracks. The two bosons in the event are measured to be longitudinally polarised, with a probability of more than 98%, as estimated using a machine learning algorithm exploiting the global kinematic properties of the event.