Measurements of four-lepton production at the Z resonance in pp collisions at √s = 7 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 mℓ+ℓ- > 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 and 8 TeV, respectively. By subtracting the nonresonant 4ℓ production contributions and normalizing with Z→μ+μ− events, the branching fraction for the Z boson decay to 4ℓ is determined to be (3.20 ± 0.25(stat) ± 0.13(syst))x 10−6, consistent with the standard model prediction.