Charmonium production in pp, pPb and PbPb collisions with CMS

Andre Govinda Ståhl,Cms Collaboration

doi:10.1088/1742-6596/832/1/012031

Abstract

The LHC Run 1 results of the analysis of charmonium production in pp, pPb and PbPb collisions with the CMS experiment are reported. The coherent J/ψ photoproduction cross section is measured as a function of rapidity in ultra-peripheral PbPb collisions at 2.76 TeV. The forward-backward ratio of prompt J/ψ yields in pPb collisions at 5.02 TeV is presented as a function of the event activity and pT. The nuclear modification factor of prompt J/ψ in PbPb collisions at 2.76 TeV is shown as a function of rapidity, centrality and pT. Finally, the ratio of ψ(2S) to J/ψ yields in PbPb collisions with respect to pp collisions at 2.76 TeV is analysed in different rapidity and centrality bins.

Highlights

Charmonium states constitute an important probe of the Quark-Gluon Plasma (QGP), since they are produced in the early stage of heavy ion collisions and their yields are sensitive to the evolution of the medium
Since the binding energy of charmonia decreases for higher excited states, it is expected that charmonium states dissociate sequentially in the QGP [1]
Summary The coherent J/ψ photoproduction cross section in PbPb ultra-peripheral PbPb collisions (UPC) is in good agreement with the leading twist approximation, indicating that shadowing effects are needed to describe the data

Summary

Introduction

Charmonium states constitute an important probe of the Quark-Gluon Plasma (QGP), since they are produced in the early stage of heavy ion collisions and their yields are sensitive to the evolution of the medium. Apart from the presence of QGP, the production of charmonium states can be altered by nuclear matter effects such as parton energy loss due to multiple scattering in the nucleus [2], or nuclear modification of the parton distribution functions (PDF) [4]. These nuclear matter effects can be studied more precisely in proton-lead (pPb) collisions and ultra-peripheral PbPb collisions (UPC), where the formation of QGP is not expected

Methods

Conclusion