Charmonium production in the TMD factorization using the Improved Color Evaporation Model

TL;DR

The paper develops a unified framework for charmonium production at small transverse momentum by pairing Soft Gluon Resummation-based TMD factorization with the Improved Color Evaporation Model for hadronization. It treats $J/\psi$ production as a convolution of TMD parton distributions with a perturbative $c\bar c$ production cross section, evolved by a Sudakov factor in $b_T$-space and supplemented by a nonperturbative Gaussian Sudakov. The hadronization probability $F^{J/\psi}$ is extracted from data at each $\sqrt{s}$, revealing a clear energy dependence, while gluon-gluon fusion dominates across the energy range and the $q\bar q$ channel becomes relatively more important at lower $\sqrt{s}$. The authors provide predictions for SPD NICA at $\sqrt{s} = 27$ GeV using $F^{J/\psi} = 0.071$, demonstrating the framework's applicability to future experiments and its potential for quantifying energy-dependent hadronization in heavy quarkonia. The work offers a consistent, first-principles-inspired approach to small-$p_T$ charmonium production with direct links to experimental observables and future collider studies.

Abstract

In the article, the study of unpolarized $J/ψ$ production in proton-proton collisions is presented. The Soft Gluon Resummation approach as a TMD framework was used for description of small-$p_T^{}$ production cross section. The Improved Color Evaporation model was considered as an approach to describe hadronization of produced quarks into charmonium state. We find that the experimental data at various center-of-mass energies $\sqrt{s}$ demonstrate the dependence of hadronization parameter $F^{J/ψ}$ on energy. The predictions for $J/ψ$ production in the kinematics of the SPD NICA experiment have been made.

Figures (3)

• Figure 1: Differential cross section of $J/\psi$ production with the experimental data of LHCb Collaboration 17 (on the left) and CDF Collaboration 18 (on the right).
• Figure 2: Differential cross section of $J/\psi$ production with the experimental data of PHENIX Collaboration 19 (on the left) and from ISR CERN 20 (on the right).
• Figure 3: Differential cross section of $J/\psi$ production with the experimental data of NA3 Collaboration 21 (on the left) and prediction for SPD NICA (on the right).