Multiparticle Collectivity from Initial State Correlations in High Energy Proton-Nucleus Collisions

Kevin Dusling,Mark Mace,Raju Venugopalan

doi:10.1103/physrevlett.120.042002

Abstract

Qualitative features of multiparticle correlations in light-heavy ion (p+A) collisions at RHIC and LHC are reproduced in a simple initial state model of partons in the projectile coherently scattering off localized domains of color charge in the heavy nuclear target. These include (i)the ordering of the magnitudes of the azimuthal angle nth Fourier harmonics of two-particle correlations v_{n}{2}, (ii)the energy and transverse momentum dependence of the four-particle Fourier harmonic v_{2}{4}, and (iii)the energy dependence of four-particle symmetric cumulants measuring correlations between different Fourier harmonics. Similar patterns are seen in an Abelian version of the model, where we observe v_{2}{2}>v_{2}{4}≈v_{2}{6}≈v_{2}{8} of two, four, six, and eight particle correlations. While such patterns are often interpreted as signatures of collectivity arising from hydrodynamic flow, our results provide an alternative description of the multiparticle correlations seen in p+A collisions.

Highlights

A remarkable series of recent experiments at CERN’s Large Hadron Collider (LHC) and at the Relativistic Heavy Ion Collider (RHIC) at BNL have demonstrated the existence of collective multiparticle dynamics in protonproton (p þ p) and light-heavy ion (h þ A) collisions
Collectivity is represented by the behavior of nth Fourier moments of the cumulants cnfmg of m-particle (m ≥ 4) azimuthal angular anisotropy correlations; it is observed that corresponding real valued mth roots of cnfmg, the anisotropy coefficients vnfmg, have nearly identical values for high multiplicity events
The collective dynamics of the latter is well described by sophisticated hydrodynamic models which presume the creation of a thermalized strongly interacting quark-gluon plasma (QGP)

Summary

Introduction

A remarkable series of recent experiments at CERN’s Large Hadron Collider (LHC) and at the Relativistic Heavy Ion Collider (RHIC) at BNL have demonstrated the existence of collective multiparticle dynamics in protonproton (p þ p) and light-heavy ion (h þ A) collisions. Hydrodynamic models have been employed to describe the experimental results on multiparticle correlations in the smaller systems. We observe strikingly that qualitative features of vnf2g and v2f4g measured in small systems are reproduced in this initial state framework.

Results

Conclusion