The production of two prompt J/? mesons, each with transverse momenta pT > 8.5 GeV and rapidity |y| < 2.1, is studied using a sample of proton-proton collisions at vs = 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/? production, is measured as a function of the transverse momentum of the lower-pT J/? meson, di-J/? pT and mass, the difference in rapidity between the two J/? mesons, and the azimuthal angle between the two J/? mesons. The fraction of prompt pair events due to double parton scattering is determined by studying kinematic correlations between the two J/? 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 seff = 6.3 ± 1.6(stat) ± 1.0(syst) mb.
Funding
ATLAS; G0275; STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCIL; ST/I006048/1