Forward J/ψ + J/ψ and J/ψ + ψ^ production with High Energy Factorization

We calculate the cross sections of associated J/ψ + ψ^ and J/ψ + J/ψ production in $pp$ collisions at √ s = 13 TeV in the forward kinematic region. The High Energy Factorization (kT-factorization) framework supplemented with the Catani-Ciafaloni-Fiorani-Marchesini evolution of gluon densities in a proton is applied. We demonstrate that latest data on J/ψ + J/ψ production and first experimental data on J/ψ + ψ^ events taken very recently by the LHCb Collaboration can be described well by the color singlet terms and contributions from the double parton scattering (DPS) with the standard choice for σeff parameter. The relative production rate σ(J/ψ + ψ⁾/σ(J/ψ + J/ψ) is found to be sensitive to the DPS terms as well as to feeddown contributions.