Albert, JustinDavid, ClaireElliot, Alison A.Fincke-Keeler, J.Hamano, KenjiHill, Ewan ChinKeeler, RichardKowalewski, RobertKuwertz, E. S.Kwan, TonyLeBlanc, Matthew EdgarLefebvre, MichelMcPherson, Robert A.Pearce, James D.Seuster, RolfSobie, Randall J.Trovatelli, M.Venturi, M.et al.ATLAS Collaboration2019-11-012019-11-0120172017Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, O.; Abdinov, O.; Abeloos, B.; … & Zwalinski, L. (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), article 76. DOI: 10.1140/epjc/s10052-017-4644-9https://doi.org/10.1140/epjc/s10052-017-4644-9http://hdl.handle.net/1828/11302The 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/ψ pT 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.enArticleDepartment of Physics and Astronomy