Associated production of $J/\psi$ pairs with the ATLAS detector
M. Watson, on behalf of the ATLAS collaboration
A recent measurement of prompt J/psi pair production is presented, using a sample of 11.4 fb-1 of proton-proton collision data collected at 8 TeV in the ATLAS detector. The differential cross-section is measured as a function of kinematic distributions for the lower-pT J/psi meson and for the di-J/psi system. A data-driven approach is used to extract the fraction of prompt J/psi pair events due to double parton scattering and an effective cross-section of double parton scattering is measured to be sigma_eff=6.3+-1.6(stat)+-1.0(syst)+-0.1(BF)+-0.1(lumi) mb.