Chan, StephenClark, Brian LeeFranklin, MelissaGiromini, PaoloHuth, JohnIppolito, ValerioLazovich, TomoLopez Mateos, DavidMorii, MasahiroRogan, Christopher S.Roloff, JenniferSkottowe, Hugh PhilipSun, SiyuanTolley, EmmaTong, BaojiaTuna, AlexanderZambito, Stefano2017-06-062017ATLAS Collaboration. 2017. “Measurement of the prompt J/ψ pair production cross-section in pp collisions at √s=8 TeV with the ATLAS detector.” The European Physical Journal C 77 (2) (February). doi:10.1140/epjc/s10052-017-4644-9.1434-6044http://nrs.harvard.edu/urn-3:HUL.InstRepos:32785057The production of two prompt J/ψ mesons, each with transverse momenta pT>8.5 GeV and rapidity |y|<2.1, is studied using a sample of proton-proton collisions at √s=8 TeV, corresponding to an integrated luminosity of 11.4 fb−1 collected in 2012 with the ATLAS detector at the LHC. The differential cross-section, assuming unpolarised J/ψ production, is measured as a function of the transverse momentum of the lower-pT J/ψ meson, di-J/ψpT and mass, the difference in rapidity between the two J/ψ mesons, and the azimuthal angle between the two J/ψ mesons. The fraction of prompt pair events due to double parton scattering is determined by studying kinematic correlations between the two J/ψ mesons. The total and double parton scattering cross-sections are compared with predictions. The effective cross-section of double parton scattering is measured to be σeff=6.3±1.6(stat)±1.0(syst) mb.en-USJournal Article2017-06-0610.1140/epjc/s10052-017-4644-9