3D Initial-State Dynamics across scales: A Comparative Study of saturation and string-based descriptions

TL;DR

This study compares string-based and saturation-based initial condition models for high-energy collisions, analyzing their applicability and differences across a wide energy spectrum.

Contribution

It provides a comparative analysis of two initial state models, SMASH and McDipper, across different energy regimes for better understanding of initial state dynamics.

Findings

Models agree at lower energies but differ significantly at higher energies.

SMASH is suitable for lower energy initial conditions in hybrid approaches.

McDipper performs well in the perturbative QCD regime.

Abstract

We compare the longitudinal deposition of various conserved quantities in the initial condition models of a string based (SMASH) and a saturation based (McDipper) approach. SMASH has been shown to work reasonably well at lower collision energies as an initial condition for the SMASH-vHLLE hybrid approach, while McDipper, based on the color-glass-condensate (CGC), works well in the regime of perturbative QCD. The two models are capable of providing longitudinally resolved initial conditions, which is essential for 3D hydrodynamical simulations. The goal of this study is to interface the different regions of applicability of the two models, to investigate the initial state dynamics in the intermediate energy regime. We analyze the deposition of transverse energy, charge and baryon number across a large range of collision energies (62.4 GeV to 5.02 TeV) and find that, while they are good agreement at lower energies, their energy and baryon deposition differs substantially at higher center of mass energies.