Impact of the Nuclear Modification of the Gluon Densities on J/Psi production in pPb collisions at sqrt(s_NN) = 5 TeV

TL;DR

This study investigates how nuclear modifications of gluon densities influence J/Psi production in proton-lead collisions at 5 TeV, using exact kinematics and yield ratios to reduce uncertainties.

Contribution

It introduces a detailed analysis of gluon PDF modifications with exact kinematics in J/Psi production, improving the understanding of nuclear effects at LHC energies.

Findings

Nuclear modifications significantly affect J/Psi yields.

Yield ratios help cancel proton-proton uncertainties.

Transverse-momentum cuts align with experimental constraints.

Abstract

We update our previous studies of nuclear-matter effects on J/Psi production in proton-nucleus for the recent LHC pPb runs at sqrt(s_NN)=5 TeV. We have analysed the effects of the modification of the gluon PDFs in nucleus, using an exact kinematics for a 2->2 process, namely g+g->J/Psi+g as expected from LO pQCD. This allows to constrain the transverse-momentum while computing the nuclear modification factor for different rapidities, unlike with the usual simplified kinematics. Owing to the absence of measurement in pp collisions at the same sqrt(s_NN) and owing to the expected significant uncertainties in yield interpolations which would hinder definite interpretations of nuclear modification factor --R_pPb--, we have derived forward-to-backward and central-to-peripheral yield ratios in which the unknown proton-proton yield cancel. These have been computed without and with a transverse-momentum cut, e.g. to comply with the ATLAS and CMS constraints in the central-rapidity region.