CERN-LHC. Measurements of the cross section for ZZ production using the 4l and 2l2nu decay channels in proton-proton collisions at a centre-of-mass energy of 8 TeV with 20.3 fb^-1 of data collected in 2012. The final states used are 4 electrons, 4 muons, 2 electrons and 2 muons, 2 electrons and missing transverse momentum, and 2 muons and missing transverse momentum (MET).
The uncertainty on the global normalisation ("Lumi") is 1.9%. See JHEP 01 (2017) 099 for more details.
The 4l channel fiducial region is defined as:
- 4e, 4mu or 2e2mu
- Ambiguities in pairing are resolved by choosing the combination that results in the smaller value of the sum |mll - mZ| for the two pairs, where mll is the mass of the dilepton system.
- ptLepton > 7 GeV (at least one with ptLepton > 24 GeV)
- |etaMuon| <2.7, |etaElectron|<2.5 (for all but one electron), |etaElectron|<4.9 (for at most one electron)
- Both lepton pairs are required to have invariant mass between 66 and 116 GeV.
- min(DeltaR(l,l)) > 0.2.
The 2l2nu channel fiducial region is defined as:
- 2e+MET or 2mu+MET
- ptLepton > 25 GeV
- |etaLepton| < 2.5
- mll must be between 76 and 106 GeV
- -MET*cos(phi_METZ)>90 GeV, where phi_METZ is the angle between the Z and the MET
- |MET - pTZ| / pTZ < 0.4, where pTZ is the transverse momentum of the dilepton system
- No events with a jet for which ptJet > 25 GeV and |etaJet| < 4.5
- No events with a third electron (muon) for which ptLepton > 7 (6) GeV
- min(DeltaR(l,l)) > 0.3