Aspects of heavy-ion collisions at the LHC

Y. Foka,G. Wolschin,L. Bravina,S. Kabana

doi:10.1051/epjconf/20147100139

Abstract

Three features of relativistic heavy-ion collisions are discussed: (1) Stopping at RHIC and LHC energies in a QCD-based model, (2) Charged-particle production in a relativistic diffusion model (RDM), and (3) Υ suppression in PbPb collisions at the current LHC energy of √sNN = 2.76 TeV.

Highlights

In this article I consider three different aspects of relativistic heavy-ion collisions
In net-baryon distributions the gluon-gluon source that is peaked at midrapidity even cancels out such that only the fragmentation sources remain [2, 3], giving rise to two fragmentation peaks that are clearly seen in the data at high SPS and RHIC energies, and in the theoretical predictions at LHC energies, see the previous chapter
The relativistic diffusion model (RDM) result for the pseudorapidity distribution of produced charged hadrons 2.76 TeV PbPb is shown in figure 6 [16] together with recent ALICE data [24] for 0−5% centrality in a χ2 optimization

Summary

Introduction

In this article I consider three different aspects of relativistic heavy-ion collisions. Results for the fragmentation peak position as function of the beam rapidity as extracted [10] from NA49 [5] and BRAHMS [6] data are shown in figure 3 [10] They fall on a straight line which agrees exactly with the analytical prediction of our partonic model based on gluon saturation [2]. In the high energy limit, the partonic model based on the concept of gluon saturation [2] predicts for the mean rapidity loss δy λ 1+λ ybeam const This result is indicated by the straight line in figure 4 for λ = 0.2 [11]. The data for the mean rapidity loss (figure 4) clearly show an increasing deviation that is indicative for the gradual onset of hadronic processes that are not accounted for in the partonic high-energy limit, and for the increasing relevance of confinement

Hadron production in heavy-ion collisions at LHC energies

RDM with three sources

Results for hadron production

Energy dependence of the three sources

Bottomium suppression in PbPb collisions at LHC energies

Bottomium wave functions

Gluodissociation in the medium

Expansion of the medium and feed-down

Results for bottomium suppression

Conclusions