Bayesian parameter estimation with a new three-dimensional initial-conditions model for ultrarelativistic heavy-ion collisions

TL;DR

This paper introduces a three-dimensional extension of the TRENTo initial-conditions model for ultrarelativistic heavy-ion collisions, enabling more realistic (3+1)D simulations and analysis at RHIC and LHC energies.

Contribution

The paper presents TRENTo-3D, a fast parametric model for 3D initial-state geometry, validated through Bayesian calibration with rapidity distribution data.

Findings

Successfully extended TRENTo to three dimensions.

Validated the model using Bayesian calibration.

Enabled future (3+1)D hydrodynamic simulations.

Abstract

We extend the well-studied midrapidity TRENTo initial-conditions model to three dimensions, thus facilitating (3+1)D modeling and analysis of ultrarelativistic heavy-ion collisions at RHIC and LHC energies. TRENTo-3D is a fast, parametric model of the 3D initial-state geometry, capable of providing initial conditions for (3+1)D models of quark--gluon plasma formation and evolution. It builds on TRENTo's success at modeling the initial nuclear participant thicknesses, longitudinally extending the initial deposition to form a central fireball near midrapidity and two fragmentation regions at forward and backward rapidities. We validate the new model through a large-scale Bayesian calibration, utilizing as observables the rapidity distributions of charged hadrons. For computational efficiency the present effort employs a (1+1)D linearized approximation of ideal hydrodynamics as a stand-in for quark--gluon plasma dynamics. This calibration serves as model validation and paves the way for utilizing TRENTo-3D as an initial-conditions model for state-of-the-art simulation incorporating (3+1)D relativistic viscous hydrodynamics.