Aad, G.Abbott, B.Abdallah, J.Abdel Khalek, S.Abdinov, O.Aben, R.Abi, B.Abolins, M.AbouZeid, O.Abramowicz, H.Abreu, H.Abreu, R.Abulaiti, Y.Acharya, B.Adamczyk, L.Adams, D.Adelman, J.Adomeit, S.Adye, T.Agatonovic-Jovin, T.et al.2016-11-232016-11-232015European Physical Journal C, 2015; 75(5):1-291434-60521434-6052http://hdl.handle.net/2440/102716The production of a Z boson in association with a J/ψ meson in proton–proton collisions probes the production mechanisms of quarkonium and heavy flavour in association with vector bosons, and allows studies of multiple parton scattering. Using 20.3fb−1 of data collected with the ATLAS experiment at the LHC in pp collisions at s√=8TeV, the first measurement of associated Z+J/ψ production is presented for both prompt and non-prompt J/ψ production, with both signatures having a significance in excess of 5σ. The inclusive production cross-sections for Z boson production (analysed in μ+μ− or e+e− decay modes) in association with prompt and non-prompt J/ψ(→μ+μ−) are measured relative to the inclusive production rate of Z bosons in the same fiducial volume to be (36.8±6.7±2.5)×10−7 and (65.8±9.2±4.2)×10−7 respectively. Normalised differential production cross-section ratios are also determined as a function of the Jψ transverse momentum. The fraction of signal events arising from single and double parton scattering is estimated, and a lower limit of 5.3 (3.7)mb at 68 (95)% confidence level is placed on the effective cross-section regulating double parton interactions.en© CERN for the benefit of the ATLAS collaboration 2015. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecomm ons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Funded by SCOAP3.Atlas CollaborationJournal article003003000510.1140/epjc/s10052-015-3406-90003556809000052-s2.0-84943162954169901