Measurements of four-lepton production in pp collisions at vs= 8 TeV with the ATLAS detector

The four-lepton (4l,l=e,µ) production cross section is measured in the mass range from 80 to 1000 GeV using 20.3 fb-1 of data in pp collisions at vs=8 TeV collected with the ATLAS detector at the LHC. The 4l events are produced in the decays of resonant Z and Higgs bosons and the non-resonant ZZ continuum originating from qq¯, gg, and qg initial states. A total of 476 signal candidate events are observed with a background expectation of 26.2±3.626.2±3.6 events, enabling the measurement of the integrated cross section and the differential cross section as a function of the invariant mass and transverse momentum of the four-lepton system. In the mass range above 180 GeV, assuming the theoretical constraint on the qq¯ production cross section calculated with perturbative NNLO QCD and NLO electroweak corrections, the signal strength of the gluon-fusion component relative to its leading-order prediction is determined to be µgg=2.4±1.0 (stat.)±0.5 (syst.)±0.8 (theory).