Rapidity dependence in holographic heavy ion collisions

TL;DR

This paper models the initial stages of heavy ion collisions using holography, then applies hydrodynamics to compare with experimental data, revealing insights into rapidity dependence and flow sensitivities.

Contribution

It introduces a holographic approach to simulate initial collision stages with decoupled longitudinal and transverse dynamics, followed by hydrodynamic evolution, to better understand rapidity dependence.

Findings

Directed flow is sensitive to viscosity.

The model qualitatively reproduces collision features.

Rapidity spectra are narrower than experimental data.

Abstract

We present an attempt to closely mimic the initial stage of heavy ion collisions within holography, assuming a decoupling of longitudinal and transverse dynamics in the very early stage. We subsequently evolve the obtained initial state using state-of-the-art hydrodynamic simulations, and compare results to experimental data. We present results for charged hadron pseudo-rapidity spectra and directed and elliptic flow as functions of pseudo-rapidity for $\sqrt{s_{NN}}=200\,{\rm GeV}$ Au-Au and $2.76\,{\rm TeV}$ Pb-Pb collisions. The directed flow interestingly turns out to be quite sensitive to the viscosity. The results can explain qualitative features of the collisions, but the rapidity spectra in our current model is narrower than the experimental data.