Studies of Z → 4ℓ decays in pp collisions at √s = 8 and 13 TeV

Z boson decays to four leptons (electrons and muons) are studied in pp collisions at √s = 8 and 13 TeV. The data, collected with the CMS detector at the LHC, correspond to a total integrated luminosity of 19.7 fb^-1 at 8 TeV and of 77.4 fb^-1 at 13 TeV. The branching fraction for all four-lepton decay modes, ℬ(Z → 4ℓ), is measured. The first measurements of the branching fractions for the decays Z → 4μ, Z → 4e, and Z → 2μ2e are also presented. Differential decay rates are measured as functions of kinematic and angular quantities in the center-of-mass frame. In addition, the first tests for CP violation in Z → 4ℓ decay, in the form of triple product asymmetry measurements, are performed. The results are compared to standard model predictions and are used to set limits on new physics in the Z → 4ℓ channel.