Study of the hard double-parton scattering contribution to inclusive four-lepton production in Collisions at TeV with the ATLAS detector

The inclusive production of four isolated charged leptons in pp collisions is analysed for the presence of hard double-parton scattering, using 20.2 ${\mathrm{fb}}^{-1}$ of data recorded in the ATLAS detector at the LHC at centre-of-mass energy $\sqrt{s}=8$ TeV. In the four-lepton invariant-mass range of $80<{m}_{4\ell }<1000$ GeV, an artificial neural network is used to enhance the separation between single- and double-parton scattering based on the kinematics of the four leptons in the final state. An upper limit on the fraction of events originating from double-parton scattering is determined at 95% confidence level to be ${f}_{\mathrm{DPS}}=0.042$, which results in an estimated lower limit on the effective cross section at 95% confidence level of 1.0 mb.