Measurement of the tt̅ Z and tt̅ W Production Cross Sections in Multilepton Final States using 3.2 fb⁻¹ of pp Collisions at √s = 13 TeV with the ATLAS Detector


The production of two prompt J/ψ mesons, each with transverse momenta p_T > 8.5 GeV and rapidity |y| < 2.1 , is studied using a sample of proton-proton collisions at √s̅ = 8 TeV, corresponding to an integrated luminosity of 11.4fb⁻¹ 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-p_T J/ψ meson, di-J/ψ p_T 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 σ_{eff} = 6.3 ± 1.6(stat) ± 1.0(syst) mb.



Proton-proton interactions, J/ψ (J/psi) meson, Transverse momentum, Large Hadron Collider (France and Switzerland)


CC BY 4.0 (Attribution), ©2016 CERN, for the ATLAS Collaboration