Prompt double $J/\psi$ production in proton-proton collisions at the LHC

Understand

We provide a detailed study of prompt double $J/\psi$ production within the non-relativistic QCD (NRQCD) framework in proton-proton collisions at the LHC.

• We confront the recent LHC data with the results obtained at leading-order (LO) in the NRQCD framework within two approaches of the collinear factorization and the $k_T$-factorization.
• We show that the LHCb data are consistent with the $k_T$-factorized LO NRQCD results.
• We show that the full LO NRQCD formalism cannot describe the recent CMS data, with about one order of magnitude discrepancy.