Particle production sources inpPb and PbPb at the LHC

Georg Wolschin

doi:10.1051/epjconf/20159001003

Abstract

Hadron production in relativistic heavy-ion collisions at LHC energies is investigated. After a brief consideration of stopping, particle production is accounted for in a nonequilibrium-statistical model with two fragmentation sources, and a central source that is mostly due to low-x gluon-gluon collisions. The particle content and energy dependence of the three sources is discussed for AuAu (RHIC) and PbPb (LHC). Results for asymmetric pPb collisions are compared with preliminary ALICE and ATLAS data. A brief survey of several features of hadron production in relativistic heavy-ion collisions at LHC energies is given in this article, which is essentially based on results pub- lished in (1), and obtained in (2, 3). The stopping process in the very first phase of the col- lision is mostly characterized by the interaction of fast va- lence quarks with low-x gluons in the respective other nu- cleus. The fragmentation peaks in net-proton (proton - antiproton) rapidity distributions are clearly visible in SPS and RHIC data (4-7). When considering rapidity or pseu- dorapidity distributions of produced charged particles, the fragmentation distributions also play a significant role, but since they shift to large values of rapidity at LHC, particle production near mid rapidity is almost exclusively deter- mined by the central low-x gluon-gluon source. This source cancels out in net-proton distributions, but in charged-hadron distributions its importance rises strongly with incident energy. In this note the relative im- portance of the three sources is investigated as function of energy from a direct comparison of the analytical solutions of a nonequilibrium-statistical relativistic diffusion model (RDM) (8) with PHOBOS (9) and recent ALICE data (10) data. This allows also for predictions at the LHC design energy, and for an analysis of the asymmetric pPb system at the current LHC energy of 5.02 TeV.

Highlights

A brief survey of several features of hadron production in relativistic heavy-ion collisions at LHC energies is given in this article, which is essentially based on results published in [1], and obtained in [2, 3]
The fragmentation peaks in net-proton rapidity distributions are clearly visible in SPS and RHIC data [4,5,6,7]
When considering rapidity or pseudorapidity distributions of produced charged particles, the fragmentation distributions play a significant role, but since they shift to large values of rapidity at LHC, particle production near mid rapidity is almost exclusively determined by the central low-x gluon-gluon source

Summary

Introduction

A brief survey of several features of hadron production in relativistic heavy-ion collisions at LHC energies is given in this article, which is essentially based on results published in [1], and obtained in [2, 3]. When considering rapidity or pseudorapidity distributions of produced charged particles, the fragmentation distributions play a significant role, but since they shift to large values of rapidity at LHC, particle production near mid rapidity is almost exclusively determined by the central low-x gluon-gluon source. This source cancels out in net-proton distributions, but in charged-hadron distributions its importance rises strongly with incident energy. In this note the relative importance of the three sources is investigated as function of energy from a direct comparison of the analytical solutions of a nonequilibrium-statistical relativistic diffusion model (RDM) [8] with PHOBOS [9] and recent ALICE data [10] data. This allows for predictions at the LHC design energy, and for an analysis of the asymmetric pPb system at the current LHC energy of 5.02 TeV

Stopping and fragmentation peaks

Hadron production sources

Asymmetric systems

Conclusion