Abstract
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 m(ℓ+ℓ(-)) > 5 GeV and 80<m(4ℓ) < 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 sqrt[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)) × 10(-6), consistent with the standard model prediction.
Highlights
A measurement of the 4l production cross section at the Z resonance provides a test of the standard model (SM) and a cross-check of the detector response to the 4l final state from Higgs decays
The results presented here include the first cross-section pmffieffi asurement of the 4l production at the Z resonance at s 1⁄4 8 TeV, and a determination of ΓZ→4l=ΓZ with improved statistical precision in a final phase-space region defined by the dilepton and four-lepton invariant mass requirements mlþl− > 5 GeV and 80 < m4l < 100 GeV, where lþl− denotes all same-flavor lepton pairs with opposite charge
Additional inelastic pp interactions are included in the simulation, and events are reweighted to reproduce the observed distribution of the average number of collisions per bunch crossing in the data
Summary
Measurements of four-lepton (4l, l 1⁄4 e; μ) production cross sections at the Z resonance in pp collisions at the LHC with the ATLAS detector are presented. This Letter presents measurements of the cross sections for the the inclusive Z resonance production of four in pp collisions at pleffispffi t1⁄4on7s
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