Double Prompt J/ψ Hadroproduction in the Parton Reggeization Approach with High-Energy Resummation.

We study double prompt J/ψ hadroproduction within the nonrelativistic-QCD factorization formalism adopting the parton Reggeization approach to treat initial-state radiation in a gauge invariant and infrared-safe way. We present first predictions for the cross section distributions in the transverse momenta of the subleading J/ψ meson and the J/ψ pair. Already at leading order in α_{s}, these predictions as well as those for the total cross section and its distributions in the invariant mass m_{ψψ} and the rapidity separation |Y| of the J/ψ pair nicely agree with recent ATLAS and CMS Collaboration measurements, except for the large-m_{ψψ} and large-|Y| regions, where the predictions substantially undershoot the data. In the latter regions, Balitsky-Fadin-Kuraev-Lipatov resummation is shown to enhance the cross sections by up to a factor of 2 and so to improve the description of the data.