$J/\psi$-meson production within improved color evaporation model with the $k_{T}$-factorization approach for $c\bar{c}$ production

TL;DR

This paper introduces an improved color evaporation model combined with the $k_T$-factorization approach to better describe $J/\psi$ production at the LHC, highlighting the impact of saturation effects and UGDF corrections.

Contribution

The study applies a new version of the color evaporation model with $k_T$-factorization and various UGDFs, incorporating recent improvements and saturation effects to enhance quarkonium production predictions.

Findings

Saturation corrections improve rapidity distribution fits.

UGDF modifications lead to better $J/\psi$ transverse momentum predictions.

Model adjustments also improve $D$-meson data description.

Abstract

We use a new approach to color evaporation model (CEM) for quarkonium production. The production of $c\bar c$ pairs is performed within $k_T$-factorization approach using different unintegrated gluon distribution functions (UGDF) from the literature. We include all recent improvements to color evaporation model. We cannot describe simultaneously mid and forward rapidity data measured at the LHC when using the KMR UGDF with the same normalization parameter. Furthermore we get somewhat too hard distribution in $J/\psi$ transverse momentum. Correcting the standard KMR distributions for saturation effects at small values of $x$ improves $J/\psi$ rapidity distributions, while taking correction for emissions hidden in the KMR UGDF in the evaluation of $x$ values improves a bit $J/\psi$ transverse momentum distributions. The modifications improve also description of the LHCb $D$-meson data.