Evolution of Anisotropy of Parton System from Relativistic Heavy-Ion Collisions

TL;DR

This paper investigates how the anisotropy of the parton system evolves in momentum and coordinate space during relativistic heavy-ion collisions, highlighting the transition from prolate to oblate shapes and the system's approach to equilibrium.

Contribution

It provides a theoretical analysis of anisotropy evolution using the free-streaming approximation, emphasizing the timing of thermalization relative to shape changes.

Findings

Momentum distribution shifts from prolate to oblate shape.

Coordinate space eccentricity decreases over time.

System reaches local thermodynamic equilibrium before momentum becomes oblate.

Abstract

Evolution of anisotropy in momentum and coordinate space of the parton system produced in relativistic heavy-ion collisions is discussed within the free-streaming approximation. The momentum distribution evolves from the prolate shape - elongated along the beam - to the oblate one - squeezed along the beam. At the same time the eccentricity in the coordinate space, which occurs at finite values of impact parameter, decreases. It is argued that the parton system reaches local thermodynamic equilibrium before the momentum distribution becomes oblate.