Topics in associated J/ψ+c+c̅ production at modern colliders

In the framework of perturbative QCD and nonrelativistic bound state formalism, we calculate the production of J/ψ mesons associated with open-charm particles at HERA and Tevatron conditions. We show that the contribution from J/ψ+c+c̅ channel becomes comparable with that of J/ψ sole production at high J/ψ transverse momenta (approximately, at p_ψ,T>10  GeV). We investigate the J/ψ polarization effects and kinematic correlations between J/ψ mesons and the accompanying open-charmed mesons. We show that the correlations are sensitive to the initial k_t of the colliding partons, and so, can be considered as an additional test discriminating the collinear parton model and the k_t-factorization approach.