Initial-state bremsstrahlung versus final-state hydrodynamic sources of azimuthal harmonics in p + A at RHIC and LHC

M. Gyulassy, P. Levai, I. Vitev, T. S. Biró

Research output: Contribution to journalArticle

2 Citations (Scopus)


Recent pT<2 GeV azimuthal correlation data from the Beam Energy Scan (BES) and d+Au runs at RHIC/BNL and, especially, the surprising similarity of 2ℓ=2, 4, -particle cummulant azimuthal n=2, 3, 4, 5 harmonics, vn{2ℓ}(pT), in p+Pb and Pb+Pb at LHC have challenged the uniqueness of local equilibrium "perfect fluid" interpretations of those data. We report results derived in [1] on azimuthal harmonics arising from non-equilibrium initial-state non-abelian "wave interference" effects predicted by perturbative QCD gluon bremsstrahlung and sourced by Color Scintillation Arrays (CSA) of color antennas. CSA are naturally identified with multiple projectile and target beam jets produced in inelastic p+A reactions. We find a remarkable similarity between azimuthal harmonics sourced by initial state CSA and those predicted with final state perfect fluid models of high energy p+A reactions. The question of which mechanism dominates in p+A and A+A remains open at this time.

Original languageEnglish
Pages (from-to)943-948
Number of pages6
JournalNuclear Physics A
Publication statusPublished - Nov 1 2014



  • Final-state viscous hydrodynamics
  • High energy nuclear collisions
  • Initial-state QCD radiation

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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