Ψ(2S) and J/Ψ modification in pPb and PbPb collisions at 5.02 TeV with CMS

Javier Martín Blanco

doi:10.1016/j.nuclphysa.2017.05.080

Abstract

The understanding of charmonium production in PbPb collisions requires the inclusion of many phenomena, such as dissociation in the quark gluon plasma and statistical recombination, on top of cold nuclear matter effects. Measurements of charmonium production in pPb collisions are crucial to disentangle the effects related to the presence of a quark gluon plasma from cold nuclear matter effects. In this paper, final prompt J/ψ results in pPb collisions at sNN=5.02 TeV are presented, including the new measurement of the RpPb using the 2015 pp data taken at the same energy. In addition, new results are reported regarding the prompt ψ(2S) meson production in pPb collisions at 5.02 TeV as a function of transverse momentum and rapidity. Final results on the relative J/ψ and ψ(2S) modification, based on the pp and PbPb data collected at 5.02 TeV by CMS in 2015, are also reported.

Highlights

Charmonium states, such as the J/ψ and ψ(2S) mesons, are excellent probes of the deconfined state of matter created in heavy ion collisions, the quark-gluon plasma (QGP)
The understanding of charmonium production in PbPb collisions requires the inclusion of many phenomena, such as dissociation in the quark gluon plasma and statistical recombination, on top of cold nuclear matter effects
The smaller J/ψ suppression observed at LHC in comparison with that measured at lower energies in SPS and RHIC, has brought to light the fact that other effects, as charmonium regeneration in the QGP or at the hadronic phase boundary, can significantly contribute to the charmonium production [2]

Summary

Introduction

Charmonium states, such as the J/ψ and ψ(2S) mesons, are excellent probes of the deconfined state of matter created in heavy ion collisions, the quark-gluon plasma (QGP). The charmonium production is sensitive to effects not associated to the presence of the QGP, such as the so called cold nuclear matter (CNM) effects. These effects include the modification of nucleon parton distribution functions when bound in a nucleus (nPDFs), energy loss and pT broadening in the nuclear medium, and nuclear absorption when passing through the nuclei [3, 4]. Other effects such as the dissociation by interactions with the co-moving matter may affect charmonium production, and are expected to be more important for less tightly bound states like the ψ(2S) meson [5]. In addition the results on the relative J/ψ and ψ(2S) modification from pp to PbPb collisions at 5.02 TeV, with integrated luminosities of 0.3 nb−1 (PbPb) and 28 pb−1 (pp), are presented [8]

The CMS detector and analysis procedure

Results in pPb collisions

Results in PbPb collisions

Summary