Speaker
Description
A wide program of studies of heavy flavour production in at LHC is performed with the ATLAS detector, including charm and beauty hadrons, quarkonia production in both sectors, and associated production $J/\psi + W$, $J/\psi + Z$ and, most recently, $J/\psi+ J/\psi$, which is the subject of this presentation.
The study is based on data collected at 8 TeV. The differential cross-section is measured as a function of the transverse momentum of the lower-$p_{\mathrm{T}}$ $J/\psi$ meson,
the di-$J/\psi$ $p_{\mathrm{T}}$ and mass, the difference in rapidity between the two $J/\psi$ mesons, and the azimuthal angle between the two $J/\psi$ mesons. The fraction of prompt pair events due to double parton scattering is determined by studying kinematic correlations between the two $J/\psi$ mesons. The effective cross-section of double parton scattering is measured to be $\sigma_{\mathrm{eff}} =6.3 \pm 1.6(\mathrm{stat}) \pm 1.0(\mathrm{syst}) \pm 0.1(\mathrm{BF})\pm0.1(\mathrm{lumi})\,\mathrm{mb}$. The total and double parton scattering cross-sections are compared with predictions.
