Inclusive production of J/ψ and ψ′ mesons at the LHC

¹ University of Rzeszów, PL-35-959 Rzeszów, Poland
² Institute of Nuclear Physics PAN, PL-31-342 Cracow, Poland

^* e-mail: acisek@ur.edu.pl

Published online: 29 November 2016

Abstract

We discuss the prompt production of J/ψ mesons in proton-proton collisions at the LHC within a NRQCD k_t-factorization approach using Kimber-Martin-Ryskin (KMR) unintegrated gluon distributions (UGDF). We include both direct color-singlet production (gg → J/ψg) as well as a feed-down from χ_c → J/ψγ and ψ′ → J/ψX. The production of the decaying mesons (χ_c or ψ′) is also calculated within NRQCD ktfactorization. The corresponding matrix elements for gg → J/ψ, gg → ψ′ and gg → χ_c include parameters of the nonrelativistic spatial wave functions of quarkonia at r = 0, which are taken from potential models from the literature. We get the ratio of the corresponding of the cross sections for χ_c(2)-to-χ_c(1) much closer to experimental data than obtained in recent analyses. Differential distributions in rapidity of J/ψ and ψ′ are calculated and compared to experimental data of the ALICE and LHCb collaborations. We discuss possible onset of gluon saturation effects at forward/backward rapidities. One can describe the experimental data for J/ψ production within model uncertainties with color-singlet component only. Therefore our theoretical results leave only a relatively small room for the color-octet contributions.