Elliptic flow due to radiation in heavy-ion collisions

T S Biró,M Horváth,Zs Schram

doi:10.1140/epja/i2015-15075-2

Abstract

In this paper we demonstrate that radiation patterns could cause flow-like behaviour without any reference to hydrodynamic description. For that purpose we use a statistical ensemble of radiating dipoles, motivated by the investigation of the equivalent photon yield produced by decelerating charges. For the elliptic asymmetry factor, v 2, we find a reasonable agreement with experimental data.

Highlights

Our goal is to demonstrate that the radiation originating from a dipole set-up is, in principle, able to match quantitatively the elliptic asymmetry factor v2, measured in heavy-ion experiments
It is noteworthy that eq (1) in the k⊥ → 0 limit reproduces a bell-shaped rapidity distribution, similar to Landau’s hydrodynamical model,and the plateau known from the Hwa-Bjorken scenario, depending whether the accelerating motion of the charge covers a short or large range in rapidity [18]
We briefly list recent literature studies about how various stages of the heavy-ion collision could contribute to the azimuthal asymmetry of the flow in order to support the phenomenological picture we sketched above

Summary

Radiation produced by decelerating sources

Parameters w1 and w2 are the boosted initial and final velocities of the charge in the frame of the observer (wi = γivi), g is the magnitude of the co-moving acceleration (c = 1). It is noteworthy that eq (1) in the k⊥ → 0 limit reproduces a bell-shaped rapidity distribution, similar to Landau’s hydrodynamical model,and the plateau known from the Hwa-Bjorken scenario, depending whether the accelerating motion of the charge covers a short or large range in rapidity [18]. Speculating further, we assume that in the case of light particles produced in a heavy-ion collision a significant part of the yield comes from similar, deceleration induced radiation processes. It is worthwhile to mention that a gauge field theory which describes the radiation phenomena on the microscopic level, can be reformulated in the framework of hydrodynamics, as it was endeavoured in refs. It is worthwhile to mention that a gauge field theory which describes the radiation phenomena on the microscopic level, can be reformulated in the framework of hydrodynamics, as it was endeavoured in refs. [19,20,21]

Elliptic flow coefficient

Fits to experimental data

Kn and

In fact experimentally

Discussion and conclusions