J/ψ -meson production within improved color evaporation model with the kT -factorization approach for cc¯ production

Rafał Maciuła,Antoni Szczurek,Anna Cisek

doi:10.1103/physrevd.99.054014

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.

Highlights

Inclusive production of quarkonia is one of the most actively studied topics at the LHC
The production of ccpairs is performed within the kT-factorization approach using different unintegrated gluon distribution functions (UGDF) from the literature
We cannot describe simultaneously midrapidity and forward rapidity data measured at the LHC when using the Kimber-Martin-Ryskin (KMR) UGDF based on the collinear MMHT2014lo parton distribution function (PDF) with the same normalization parameter

Summary

INTRODUCTION

Inclusive production of quarkonia is one of the most actively studied topics at the LHC. It was shown recently that the LHC data can be explained within the NRQCD kT-factorization approach with a reasonable set of parameters [5] Another popular approach is the color evaporation model (CEM) [6,7]. The computations of the transverse momentum dependence of J=ψ meson production within the color evaporation model are based on the collinear approach up to the next-to-leading order (NLO) [11]. The kT-factorization with the Kimber-Martin-Ryskin (KMR) unintegrated distributions turned out to be successful in the description of the inclusive production of D mesons [16,17] as well as for some correlation observables [16,18] at the LHC It seems interesting, and valuable, to apply the kT-factorization approach for ccproduction in the context of the color evaporation model for J=ψ meson production In the present paper we wish to study whether such a combination of elements can allow one to describe the world data for prompt J=ψ production.

THEORETICAL FRAMEWORK

NUMERICAL RESULTS

CONCLUSIONS