Measurements of Four-Lepton Production at the Z Resonance in pp Collisions at √s=7 TeV and 8 TeV with ATLAS

Measurements of four-lepton (4l, l = e, μ) production cross sections at the Z resonance in pp collisions at the LHC with the ATLAS detector are presented. For dilepton and four-lepton invariant mass regions mll > 5 GeV and 80 < m4l < 100 GeV, the measured cross sections are 76 +-18(stat)+- 4(syst)+- 1.4(lumi) fb and 107+-9(stat) +- 4(syst)+- 3.0(lumi) fb at √s=7 TeV and 8 TeV, respectively. By subtracting the nonresonant 4l production contributions and normalizing with Z → μμ− events, the branching fraction for the Z boson decay to 4l is determined to be (3.20+-0.25(stat)+-0.13(syst))×10−6, consistent with the standard model prediction.