Elliptic flow at varying energy heavy ion collisions: Partonic vs hadronic dynamics

Abstract

We examine whether the breakdown in elliptic flow quark number scaling observed at the Relativistic Heavy Ion Collider (RHIC) energy scan is related to the turning off of deconfinement by testing the hypothesis that hydrodynamics and parton coalescence always apply, but are obscured, at lower energies, by variations in the widths of quark and anti-quark rapidity distribution. We find that this effect is enough to spoil quark number scaling in elliptic flow. A lack of scaling in data therefore does not signal the absence of partonic degrees of freedom and hadronization by coalescence. In a coalescing partonic fluid, however, elliptic flow of anti-baryons should be the greater than that of baryons, since antibaryons contain a greater admixture of partons from the highly flowing midrapidity region. Intriguingly, purely hadronic dynamics has a similar dependence of baryon-anti-baryons $v_2$ as purely partonic dynamics, again because antibaryons tend to come from regions where the deviation of the system from hydrodynamic behavior is at its smallest. The opposite trend observed in experiment is therefore an indication that we might be misunderstanding the origin of $v_2$. We finish by discussing possible explanations of this, and suggest experimental measurements capable of clarifying the situation.

Final version, to be published by PRC Some clarification and correction in the discussion, typos in equations fixed

References in corpus (15)

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• Scaling properties of azimuthal anisotropy in Au+Au and Cu+Cu collisions at sqrt(s_NN) = 200 GeV
• Nonperturbative Heavy-Quark Diffusion in the Quark-Gluon Plasma
• Multiplicity scaling in ideal and viscous hydrodynamics
• Coalescence Models For Hadron Formation From Quark Gluon Plasma
• Scalings of Elliptic Flow for a Fluid at Finite Shear Viscosity
• Constituent quark scaling violation due to baryon number transport
• Effects of hadronic potentials on elliptic flows in relativistic heavy ion collisions
• Second order dissipative fluid dynamics from kinetic theory
• Core - Corona Model describes the Centrality Dependence of v_2/epsilon
• Scaling of $v_2$ in heavy ion collisions
• Unruh gamma radiation at RHIC?
• Phase-Space Coalescence for heavy and light quarks at RHIC
• The elliptic flow in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5 and 39 GeV at STAR
• Properties of the partonic phase at RHIC within PHSD

Cited by in corpus (10)

• Elliptic flow of identified hadrons in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7--62.4 GeV
• Elliptic flow splitting as a probe of the QCD phase structure at finite baryon chemical potential
• Elliptic Flow of Protons and Antiprotons in Au+Au Collisions at $\sqrt{s_{NN}}$ = 7.7--62.4 GeV within Alternative Scenarios of Three-Fluid Dynamics
• Blast Wave Fits to Elliptic Flow Data at $\sqrt{s_{\mathrm{NN}}}=$ 7.7--2760 GeV
• Isospin splitting of pion elliptic flow in relativistic heavy-ion collisions
• Collision energy dependence of elliptic flow splitting between particles and their antiparticles from an extended multiphase transport model
• Azimuthal instabilities of the Gribov-Levin-Ryskin equation
• Elliptic flow splittings in the Polyakov-looped Nambu-Jona Lasinio transport model
• Scaling of flow in heavy ion collisions and the low-energy frontier
• Scaling of elliptic flow in heavy ion collisions