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Interpretations of the most recent experimental data on double J/ ψ production are discussed. It is shown that a significant signal in the region of high invariant masses of a J/ ψ pair may be a piece of evidence not only in favor of the dominance of double parton scattering in this region. The diagrams involving two-gluon exchange in the t channel, which are considered in the present study, make a commensurate contribution to the above production process in the region in question and also to the double production of J/ ψ mesons characterized by a large rapidity difference. [ABSTRACT FROM AUTHOR]

Light hadrons provide a convenient tool for studying the properties of hot and dense media formed in central collisions of relativistic heavy nuclei. The results obtained in the PHENIX experiment at the relativistic heavy-ion collider (RHIC, Brookhaven National Laboratory, USA) by measuring nuclearmodification factors for light hadrons in various colliding systems ( pp, dAu, CuCu, and AuAu) at the c.m. energies of √ s = 62.4 and 200 GeV are presented. [ABSTRACT FROM AUTHOR]

The inelastic photo- and electroproduction of J/ψ mesons at the HERA collider are considered within the semihard (kT-factorization) QCD approach and the color-singlet model. The total, differential, and double-differential cross sections for the inelastic production of J/ψ mesons are investigated versus the Pomeron intercept Δ, which is the basic parameter of low-x physics; also studied here is the spin alignment parameter α versus the square of the transverse momentum, pψT², and the variable z. The theoretical results obtained in the present study are compared with the latest experimental data of the H1 and ZEUS Collaborations. It is shown that experimental investigations of the polarization properties of J/ψ mesons at the HERA collider for Q² < 1 GeV² may provide an additional test of the Balitsky-Fadin-Kuraev-Lipatov dynamics of gluon distributions. [ABSTRACT FROM AUTHOR]