Inclusive $J/\psi$ productions in pp collisions at $\sqrt{s}=$ 5.02, 7, and 13 TeV with the PACIAE model

Abstract

We investigate the inclusive $J/\psi$ production in proton-proton (pp) collisions at center-of-mass energies $\sqrt{s} = 5.02$, 7, and 13 TeV using the PACIAE 4.0 model. This model extends PYTHIA 8.3 by incorporating partonic and hadronic rescatterings before and after hadronization, respectively. Compared to our earlier study [K.-F. Ye et al., Phys. Rev. C 109, 035201 (2024)], which considered only the color-singlet processes, the present work includes both the color-singlet and color-octet contributions within the non-relativistic QCD (NRQCD) framework. In addition to NRQCD, we also consider the contributions from the cluster collapse and weak decays of $b$-hadrons. We find that the simulated inclusive $J/\psi$ transverse momentum differential cross sections agree well with the experimental data at both the middle and forward rapidities. We provide a quantitative analysis of the relative contributions for different production mechanisms and their energy and rapidity dependence in the inclusive $J/\psi$ production. Furthermore, we offer a quantification of the relative contributions of the various components and their energy and rapidity dependence in the NRQCD channels, including the direct production via the hard scattering and the feed-down from the decays of heavier charmonium states such as $\psi(2S)$, $\chi_{c0}$, $\chi_{c1}$, and $\chi_{c2}$. Finally, we examine the effects of partonic and hadronic rescatterings and offer the quantitative estimate of their impact on the $J/\psi$ production. These results are entirely new and represent a significant step forward in understanding the mechanisms of the inclusive $J/\psi$ production in high-energy pp collisions.