Pre-hydrodynamic evolution and its impact on quark-gluon plasma signatures

TL;DR

This paper introduces a new kinetic model, K_TIso, for the early pre-hydrodynamic stage in heavy-ion collisions, allowing for initial momentum anisotropies and assessing their impact on observable signatures.

Contribution

The paper presents K_TIso, a novel computational module that models pre-hydrodynamic evolution with initial momentum anisotropies, improving understanding of early-stage dynamics in heavy-ion collisions.

Findings

Initial momentum anisotropies influence hadronic observables.

K_TIso efficiently models early-stage evolution with anisotropies.

Pre-hydrodynamic scattering affects final collision signatures.

Abstract

State-of-the-art hydrodynamic models of heavy-ion collisions have considerable theoretical model uncertainties in the description of the very early pre-hydrodynamic stage. We add a new computational module, K$_\mathrm{T}$Iso, that describes the pre-hydrodynamic evolution kinetically, based on the relativistic Boltzmann equation with collisions treated in the Isotropization Time Approximation. As a novelty, K$_\mathrm{T}$Iso allows for the inclusion and evolution of initial-state momentum anisotropies. To maintain computational efficiency K$_\mathrm{T}$Iso assumes strict longitudinal boost invariance and allows collisions to isotropize only the transverse momenta. We use it to explore the sensitivity of hadronic observables measured in relativistic heavy-ion collisions to initial-state momentum anisotropies and microscopic scattering during the pre-hydrodynamic stage.