Elliptic flow of gluon matter in ultrarelativistic heavy-ion collisions

TL;DR

This paper uses a perturbative QCD-based parton cascade to calculate the elliptic flow of gluon matter in heavy-ion collisions, comparing results with experimental data and discussing implications for the quark-gluon plasma's properties.

Contribution

It provides a detailed calculation of gluon elliptic flow using a parton cascade model and explores the effects of hadronization and freezeout conditions on flow measurements.

Findings

Integrated v2 matches experimental data.

Gluon v2(pT) is 20-50% smaller than data.

Hadronization processes are key to explaining v2(pT) jump.

Abstract

Employing a perturbative QCD based parton cascade we calculate the elliptic flow $v_2$ and its transverse momentum dependence $v_2(p_T)$ for the gluon matter created in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. To make comparisons with the experimental data at the BNL Relativistic Heavy Ion Collider (RHIC), parton-hadron duality is assumed. We find that whereas the integrated $v_2$ matches the experimental data, the gluon (or pion) $v_2(p_T)$ is about 20-50% smaller than the experimental data. Hadronization via gluon fragmentation and quark recombination seems to be the key to explaining the necessary jump of $v_2(p_T)$ from the partonic to the hadronic phase. We also show that the elliptic flow values moderately depend on the chosen freezeout condition, which will thus constrain the shear viscosity to the entropy density ratio of the quark gluon plasma created at RHIC.