Investigating the impact of the gluon saturation effects on the momentum transfer distributions for the exclusive vector meson photoproduction in hadronic collisions

V.P Gonçalves,F.S Navarra,D Spiering

doi:10.1016/j.physletb.2017.03.009

Abstract

The exclusive vector meson production cross section is one of the most promising observables to probe the high energy regime of the QCD dynamics. In particular, the squared momentum transfer (t) distributions are an important source of information about the spatial distribution of the gluons in the hadron and about fluctuations of the color fields. In this paper we complement previous studies on exclusive vector meson photoproduction in hadronic collisions presenting a comprehensive analysis of the t-spectrum measured in exclusive ρ, ϕ and J/Ψ photoproduction in pp and PbPb collisions at the LHC. We compute the differential cross sections taking into account gluon saturation effects and compare the predictions with those obtained in the linear regime of the QCD dynamics. Our results show that gluon saturation suppresses the magnitude of the cross sections and shifts the position of the dips towards smaller values of t.

Highlights

Experimental results released in the last years have demonstrated that photon – induced interactions in hadronic collisions can be used to probe several aspects of the Standard Model (SM) as well as to test predictions of Beyond SM Physics (For a recent review see Ref. [1])
In Refs. [6, 11] we demonstrated that the experimental LHC Run 1 data and the preliminary Run 2 data can be sucessfully described within the color dipole formalism if non - linear effects in the QCD dynamics are taken into account
In order to investigate the impact of the gluon saturation effects, associated to non linear contributions for the QCD dynamics at high energies, we will compare our predictions with those obtained disregarding these effects, i. e. using a linear model for the QCD dynamics

Summary

INTRODUCTION

Experimental results released in the last years have demonstrated that photon – induced interactions in hadronic collisions can be used to probe several aspects of the Standard Model (SM) as well as to test predictions of Beyond SM Physics (For a recent review see Ref. [1]). The t - distributions may be measured in Run 2 [1] This encourages us to extend our previous studies and present the color dipole predictions for the t – spectrum measured in exclusive vector meson photoproduction in hadronic collisions. In this paper we will use the color dipole formalism to describe the photon - hadron interaction, with the scattering amplitude being expressed in terms of the impact parameter Color Glass Condensate (bCGC) model, which successfully describes the t - distributions for the exclusive vector meson production at HERA.

FORMALISM

RESULTS

CONCLUSIONS