Highly-anisotropic and strongly-dissipative hydrodynamics with transverse expansion

TL;DR

This paper extends the ADHYDRO framework to include asymmetric transverse expansion, compares model predictions with RHIC data, and finds that certain observables are insensitive to initial pressure anisotropy, implying delayed thermalization.

Contribution

The paper introduces new developments in ADHYDRO, including asymmetric transverse expansion and comparison with experimental data, highlighting the insensitivity of observables to initial anisotropy.

Findings

Observables are insensitive to initial pressure anisotropy.

Thermalization may be delayed to about 1 fm/c.

Model agrees with RHIC data for various soft-hadronic observables.

Abstract

A recently formulated framework of highly-anisotropic and strongly-dissipative hydrodynamics (ADHYDRO) is used to describe the evolution of matter created in ultra-relativistic heavy-ion collisions. New developments of the model contain: the inclusion of asymmetric transverse expansion (combined with the longitudinal boost-invariant flow) and comparisons of the model results with the RHIC data, which have become possible after coupling of ADHYDRO with THERMINATOR. Various soft-hadronic observables (the transverse-momentum spectra, the elliptic flow coefficient v_2, and the HBT radii) are calculated for different initial conditions characterized by the value of the initial pressure asymmetry. We find that as long as the initial energy density profile is unchanged the calculated observables remain practically the same. This result indicates the insensitivity of the analyzed observables to the initial anisotropy of pressure and suggests that the complete thermalization of the system may be delayed to easily acceptable times of about 1 fm/c.